Do bowstrings override bowstrings?

I found a lovely bow (15-28 req.8 13%^50 +5 defence always) Only one problem it has a crappy +1 -1 vamp. If I put a different bowstring on it will it overide the vamp?

yup

The same applies for every mod.
Haft for Haft and Grip for Grip. Careful what you do.