Compression should be checked with the engine COLD! Not -40F cold but at ambient temperature.

It can be tested through the glow plug ports using the proper adapter eliminating the need of dealing with fuel return lines and heat shields. You need to remove the hard lines whether you test through the ports or injectors.

Valve adjustment is always a good idea. Timing chain stretch, unless extremely excessive, will have minimal effect on compression. Good idea to check since you will have the valve cover off anyway.

Timing chain stretch will affect performance and starting and would have to be extreme to be detected by a compression test.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now