Your friend will need a chain tool to cut the new chain to length. I would also suggest that he get a chain with a "master link" for joining it; I find the Shimano "special joining pin" concept to be flawed. SRAM, KMC and Wippermann offer chains with the connecting link included.

If the chain is significantly worn a new one may not play well with a similarly-worn cassette/freewheel, which may also need to be replaced. If the chain does not skip then it will be fine, otherwise replace it. Your friend should be prepared for this possibility