Matthew,
Welcome to the Forum. I'd be cautious in accepting any advice concerning not worrying about the chain and tensioner. The only way to know how much chain stretch you may have is to check it. A shot in the dark from someone who has not examined your engine is just that.
I've measured mine at 100K and it has some stretch that is clearly measureable. Addtionally, although the chain in the M119 engine is reportedly pretty reliable, the chain guides (made of some sort of plastic/composite) get brittle, can break, and can fall into the chain sprockets... dislodging the chain and destroying the engine.
Folks that don't believe the M119 can fail can look at this ad from eBay last week for a 1999 M119 with a bad chain. Went unsold for $500 starting bid because its probably worthless. This motor had 124K on it when it failed.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7953400608&category=33615
Go price a replacement for your engine, measure that against the cost of getting it checked, and then make your decision. If you're going in for service anyway, why not get it checked?
Good luck with your coupe. Nice car.
