Changing your perks is just a matter of levelling enough. You get a new perk card at every level, chosen from the cards offered to you by the game and the choice increases with every level up to 50 (EDIT: because at L50 you'll have the whole pack to choose from). You can swap perks in and out of play at any time. So if, for example, you took 3 Armorer perk cards and then decided you didn't want Armorer after all because you'll be using power armor all that means is that you'll take Armorer out of your cards in play and replace it with some other cards. At most, you'll need to gain 3 more levels to choose the cards you want to replace Armorer (although you might find some useful cards already in your hand from the randomly chosen perk card packs put into your hand at various levels up to 50).
You can respec your perks at any time at any level and without even levelling up. You'll have a hand of cards, some of which you chose as you levelled and some of which were added to your hand by perk card packs at various levels. At any time, you can respec your perks with any perks for which you have the cards in your hand. For example, I usually play with Enforcer 3 and Action Boy 3 agility perks, but I respec to Action Boy 3 and Ammosmith 1 while I'm crafting ammo and then back to Action Boy 3 and Enforcer 3 afterwards. When I gain some more levels and I have some cards I want more, I will take Ammosmith 2 more times so I can swap Enforcer 3 and Ammosmith 3 back and forth in the same way.
The problem is changing your SPECIAL stats. Or rather, it might be. If you want to change a perk in one stat for a perk in the same stat, there's no problem. If you want to change a perk in one stat for a perk in a different stat, there might be a problem because you can't simply swap your SPECIAL stats like you can your perks.
After L50, you have a choice at each level. You can either take another card from the pack and add it to your hand or you can take a SPECIAL point from one stat and add it to a different stat.
I'd advise using a build planner to plan out the build you want and see how much the SPECIAL stat requirements for that build vary from what you've already got and how much the perk cards vary from what you've already got (in your hand, not in play) to work out how many extra levels you'll have to gain in order to get the SPECIAL stats and perks you want. But it will be solely a matter of gaining more levels.
For example, I've chosen to have an endurance of only 3 because I decided that other perks in other stats were more important than perks in endurance. I currently just have a couple of placeholder perks in endurance that are of minimal use. When I pass L50, I'll choose Lifegiver cards to put in endurance to add to my HP. However...I'm finding that I quite often get infected with diseases from mobs attacking me and endurance affects disease resistance. So I might decide that higher endurance is more important than a different stat. I have 11 intelligence, but the int perks I want on while I'm playing only use 8 points. The other 3 int I'm using for perks I use while crafting, so I don't actually need those 3 extra int points. Int probably directly affects the condition and durability of crafted items, but reducing it from 11 to 8 might be outweighed by the increased disease resistance from increasing endurance from 3 to 6. I might decide to reduce my int to 8 and increase my endurance to 6. If I do, all that will mean is that I will need to gain 3 more levels (above L50).
You're never completely locked into any build. Changing your build is always a matter of levelling some more or just swapping perk cards in and out if you already have them in your hand and you don't need to change stats. For example, I have a strength of 12, which I'm currently using for shotgun perks because my current build uses a rifle for distance and a shotgun for close range. 12 is enough to make a decent heavy weapons or melee build. I could pick heavy weapons perk cards as I level and then I could swap between a rifle/shotgun build and a heavy weapons build any time I liked. I could also pick melee perk cards as I levelled and swap between rifle/shotgun, heavy weapons and melee builds any time I liked. I'd just need enough levels to pick enough cards to give me those choices.
I'm curious as to why, unless you're not using power armour and have a lot of unpowered armour with a L25 level requirement and a couple of very heavy weapons with a L25 requirement. Power armour weighs 10 on a chassis and you can always put power armour on a chassis even if you can't use it.
Your turrets don't give you XP. They'll only help with that if you're present during an attack and hit an attacker yourself. Then you'll get xp, even if your turrets did almost all of the damage. The main reason quite a few people camp on Whitesprings golf course is that it's relatively safe from attacks by mobs because the whitesprings guard robots tend to do a good job of dealing with them. It's also a mostly flat area, so it's convenient for building, and it cuts fast travel costs to camp there while
you're using the Enclave bunker hidden under it, which you'll be doing a lot in the endgame
The drawbacks of camping on the Whitesprings golf course are (1) the area is quite often nuked and (2) malicious players who enjoy spoiling other people's enjoyment tend to go there to find camps to destroy because it's a good place to find camps.
I am starting to find Excavator mods around it now.
Its a real hard mission though 
designed for 4 players really.
then got killed several times & lost some of my inventory as well 
An old reference and an ancient reference in one reply. Eh...when I were a lad 
