I did some research and there are 3 parts I believe I could exchange:
Nut
Bridge
Stop tail piece
All three would require me to go to a skilled luthier and imply quite a lot of cost.
I'm not sure why you think changing the tailpiece or bridge would need the involvement of a skilled luthier - parts are made to pretty standard sizes nowadays and I think the ABM and Gotoh parts
probably even use the same metric thread sizes on their mounting screws (I'm not totally sure about that, but I assume ABM, being German, use metric sizes).
It's true that your bridge uses the larger posts which are perhaps a little less common than the narrower types, so that might be a bit of an issue.
As to the effects of actually changing the parts, they will be fairly subtle. I've often swapped standard tailpieces for lighter aluminium ones, which does make a noticeable difference - high and low notes seem to ring out a little more, become more "piano-like". On the other hand I think it sometimes seems to take away a little solidity in the midrange, and I'm not convinced it helps sustain (perhaps even the opposite).
Changing the bridge won't make so much difference unless you get one made from a totally different material. I believe most are made from zinc or similar; you might find some brass ones, or Callaham make one from solid stainless steel. Graphtech's ResoMax bridges are made from some kind of lightweight alloy and they would also directly replace your Gotoh parts, without any surgery:
http://www.graphtech.com/products/brands/resomax/resomax-tune-o-matic-bridges