Things to always look out for with these:
1. Inspect the motherboard! If your 1200 still has its RF shield it means removing it. The smt capacitors on these machines leak, they can eat/damage cicruit traces.
There are some amazing people out in retroland who can repair and upgrade all sorts, so if you care unable to do it yourself! there is somebody who can
2. Inspect the psu. If the psu has RIFER power filter caps, they can let go without warning. They tend to just pop, let out magic smoke and make the whole place stink. The good part is they can be replaced and afaik cause no damage.
There is lots of debate revolving around Retrobriting. It works and the results can be amazing! but it does not last!
I love these machines. the holy grail for me is the A1000 and is the one amiga I have never owned.