on 35mm drop you should be fine, i did 40mm drop on my old mk4 and it was ok... but occasionally on hard cornering it would scuff the antiroll bar on the drive shafts... (40mm or lower and you need a diffo anti roll bar or a drop link thing like joe mentioned... i bought a neuspeed anti roll bar which transformed the handling when i fitted coilovers a few months later.....)
to do it diy is easy... the rears you can do in about 1/2 hour as its just a case of dropping the rear shocks (2 x 17mm bolts both sides whilst the rear jacked up) the remove old springs and fit new..., the fronts are a bit harder... need to undo to nut (buzz gun), then lower bolt on hub carrier... but chances are it will be rusted/corroded into hub carrier to youull need to knock it out... clean it all up, strip the strut (after compressing spring) then remove boat like spring, and rebuild with lowered spring.... then once all assembled take to a garage and get tracking/alignment done so no bad scrubbin....
job done
or pay some one to do it....
