Gutentaug and welkommen Kaleun!
Now GWX is an absolute realism mod. Ships that were in port during the war are now in port during GWX campaigns. Royal oak being sunk by U-47 in scapa flow for example! I was told to stay with the stock campeign too before going with GWX. I would skip that advice and go straight to GWX 3.0! Its not alot harder but it is much much more realistic. It will bump up your loading times quite a bit but other than that graphically speaking it isnt that off from stock.
Yes I would absolutely say go for it. And I bought a GeForce 7300GT w/512 megs of graphics memory in AGP for fairly cheap recently. So there are options out there for AGP users.
But my point, GWX 3.0 I wouldnt hesitate.
and welcome aboard, Let me buy you a beer!