Drain the fuel, put new fuel in and filters. Check the transmission fluid. If the car doesn't wanna move, I've had the displeasure of discovering bone dry fluid with a trans that didn't wanna move. If it's dry you're gonna burn up the converter trying to move it and drive it with no fluid.

Valve adjustment isn't a bad idea, you need feel gauges though.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k