I have a diesel garden tractor; the OM603 engine is definitely more complicated but still mostly mechanical.
............................................................
The 300TD (wagon) tends to sell for a higher price -- unless you need/want a wagon for some reason, consider a sedan. Buy the one with the best set of service records. An engine with a #14 (earliest version) head can still be OK, it is more at risk of cracking if the engine is overheated than the later versions of the head. If the engine is not overheated, no problem regardless of the head number.

At 300,000 miles the transmission will be in need of an overhaul if it has not already been done. Budget about $3000 for that. The engine will still be OK at 300,000 if it has been well cared for. The timing chain would be my only concern and that's not a big job. Consider investing in a compression/leakdown test before you buy. About $500 to have a mechanic do it (California prices), much cheaper if you can do it yourself.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970