Your chain can become stretched to the point of needing replacement. Also the tensioner can become weak. IMO, if the chain is stretched, just buy a new motor from Soko and swap it in. As big of a bitch as it is to swap the chain with the motor in the car, and the other wear on the engine if it is stretched (not that a stretched chain caused it, just if your engine has that many miles it's probably pretty tired, swap it out and rebuild it with high compression, cams, etc), it would take about the same amount of time and money to do a motor swap if you're going to buy all the stuff you should replace on the motor with the chain (guides, tensioner, etc). A slightly used motor from Soko is $395 right now.
Keep in mind though that there are guys with cars over 200K that run 14s.
Also, I doubt your chain is stretched though, they're pretty tough. The tensioner has been upgraded, though. I prolly need one on my SE-R, as it has a wicked chain slap on start up (no oil pressure leaves the tensioner too loose I guess and the chain makes all kinds of racket for 2 seconds on startup). The tensioner isn't too expensive to replace.
Did someone tell you your belt [chain] needs to be replaced? If it was your mechanic, stop seeing him.
Tom