The back wheel was stolen and the bike shop put a 7-speed cogset on the new wheel. (I didn't know better at the time, but I later realized that it had been an 8-speed before.)
You need a chain pin tool to remove the old chain and 'cut' the new chain to the correct size.
Will any chain tool work? Also, I'm not sure what you mean by "cut"--could you explain?
Thanks!