He wants to trade for your car? So no cash? What kind of car do you have? I'd seriously consider having a mechanic overlook the car first since you don't seem to know too much, and I don't mean that to sound negative. Sounds like this car might have a whole lot more problems then this guy is alluding to.
my car is a 99 civic coupe clean but idles wierd and grinds into 3rd. and possibly a headgasket problem developing casuing the idle but im not sure. he will put cash on top. and i dont mind changing the timing chain im just worried if i change it and end up not fixing it. making sure that what he sais its doing is a timing chain problem and that a new one will fix it.
if the timing chain skipped more then one tooth don't bother it bent the valves and you'll need a brand new head. if it isn't misfiring or sputtering then it just skipped one tooth and the ecu is compensating for it and your valves should be OK. But don't get into thinking that its an easy 30min fix, if you don't work on cars then don't buy this car.
Since you don't have any reference to vr's, then really just if it misfires or is really poor acceleration then it skipped more then one tooth. it will also throw a code out if you scan it that shows if the cams slipped. The more teeth it slipped the worse it will be but you should be able to tell if it skipped cause it will run like ****