I'm looking at a 2003 GMC DMAX or a 2002 CHEV DMAX. Both are about 50000 mi. CC, Long Bed, 2500 HD. What are the small and big things I should look for? Any advice would be great. Thanks.

Check the oil to see if you can smell or see any diesel on the dipstick.
Personly I would go for the 2002 if they are both the same condition.
Statisticly the 2002 has less problems.
Look for any mods that are on or were on the truck. Like exhaust, pyrometer probe on the passanger side exhaust manifold, air intake, gauges, etc. This should give you a good idea on how the truck was used.
Check the fluid in the tranny to see if smells burnt. Take them for a test drive and if possible get on it as hard as you can just to see if the truck goes into limp mode. If it does with no additional mods than the tranny needs help bad. Just an FYI.

Get the VINs and run a VIN Check here on the board to see what problems have been handled by GM.

Get the truck checked for fuel or antifreeze in oil(injectors/head gasket). Also leaks at the transfer case and axel seals (known issues). Buy the truck with the best warranty in the best shape. Get a good diesel shop to check it over.

Great !! Thanks for the replied so far, keep em coming.
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