^disagree with the last two - a maintained E30 should last well past 300k. also, though i have not looked up the blue book for this one, the values tend to be quite off for E30s.
$2800 seems somewhat high to me. you might be able to talk him down some, but he's obviously put some work into it (note rims, new paint, lowered, etc) and might want to get some of that money back out of it. to give you some idea of price, mine was $3600, had a spotless interior, 170k miles, and minimal rust. also, it's a 5-speed AWD, which is rare. the 325is is fairly and could make a good track car, but not for $2800 in that condition, IMO.
other than that, listen to witeshark. and actually, just go ahead replace the timing belt anyway.