UPDATE:

1.) 2000 V6 Xterra is NOT an interference engine (as best I can tell)
2.) Compression test was silly idea, since if intake valves can't open/close no air can get in so won't build compression. My thinking was that some cylinders would have all valves closed and I'd get compression, but no working intake means that isn't valid...

Cams are VERY hard to rotate with any pressure on valves, so they tend to wind up in an all-closed position: good news for anyone who breaks a timing belt means VERY good chance cam will quickly stop with all valves closed (ie. mechanically unlikely that it will come to rest with valves open).

Put #1 at TDC using borescope to make absolutely sure at absolute TDC, then rotated cam and could easily rotate cam through several rotations (using a socket). Does not appear that valves touch piston (at least nothing that prevented me from rotating cam 360 deg).

borescope was helpful in that I could confirm (can see both valves using the angle mirror on the scope) that all vavles were closed, so that made me feel more confident in taking the time to pull the timing cover. Also, didn't see any signs of valve hit on the pistons, but piston was surprisingly hard to see (could not see all of the piston surface)

Anyway, if you break your timing belt there is a very good chance your valves survived, and IMHO it would be worth replacing the timing belt and see if it runs (mine runs great).