Try lubing the chain well and wiggling it around. If it loosens up and doesn't have any kinks, and shifts smoothly, you might not need to replace it. Poor shifting doesn't have to mean the chain is worn either, just that the derailleur wire needs tightening.
If you do need to replace it, tell the bike shop how many cogs the bike has in back, that determines the width of the chain. If it's 18 gears you either have 2 in front and 9 in back, or 3 in front and 6 in back.
I love that you're fixing up an old bike for someone
Last edited by lph; 04-21-2012 at 08:14 AM.
Reason: cogs, was the word I was looking for
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett