Sure. My SS were horrible in the wet before I had 'em siped; Great after...
I imagine you could do it with a utility knife, but be prepared to have sore arms after. I've always had mine done; Pretty cheap-something like $12 a tire at Les Schwab & they don't remove a bunch of material...
Shouldn't matter if it's a retread or not...
Won't have much, if any, affect on the noise; That's caused by the design of the tread & hardness of the rubber vs. the road material... <img src="/forums/images/graemlins/cheers.gif" alt="" />

4xGeek (Chris)
'97 T-100 4wd sr5-suto, 3" BL, 1.5" BJ spacers, 35" ProComp AT's, 4.88's, Bilsteins x 6, etc...

No longer stuck in SoCal!! smile