When in game and I die can I change my class if so what key or option allows this?
Yes, hit the caps lock key, it displays almost everything you need to control. Weapons, squads, teams etc. If your squad leaders. commander you can control your team from there too.
If I die can I always be rez'd by a medic or do you have to do something to try to get a medics attention?
As long as it says your critically injured you can be revived, if your killed then you have to respawn. You dont have to do anything to be allowed to be revived, although by clicking you mouse button you shout "MEDIC NEEDED" which might attract someones attention.
Does the sniper rifle have variable zoom when in scope mode?
No, not as far i know, but i dont snipe much so someone else could answer it better than me.
Can you unlock night vision scopes?
I think that will be in the special forces mod if its possible. Ive certainly never seen it in BF2.
Mega slow loading of a level?
Yes, mine takes a good 3 or 4 minutes to load. Generally if it hangs in the 60% range i think it means its optimizing the shaders for your game, it should only hang there if you change your graphics settings. It takes ages once its loaded and says varifying information for me.