Shorter 'sport' springs require different length shocks, they are inside of the springs. If the rear is still 'normal', then the owner cheated and wanted a quarter mile car, not something that handles well in curve. Easy enough to verify, just meansure from the center cap to the top of the wheel well. The front and rear should have the same measurement, within 1/2 inch or so.

Valve guides shouldn't be a problem, it is the valve stem seals that get old and allow vapor/oil to pass through to the cylinder. Ask if all of the valves have been replaced, not just the damaged ones - remember, there are 20 of them.

New valves would require guides and seals.

The turbo is no big deal. The Mitsubishi will last as long as the rest of the engine. The internal oil seal in the intake side tends to wear and pushes a very small amout of air/oil into the intake stream after about 80K or so. Most T5 owners install a 17G turbo for more boost.

The block/crank/pistons should be good. I would still ask for a compression test readout, I don't trust boring cylinders and rings. Is that for all cylinders, or just the damaged one??? The oil light should go out immediately after engine start, no waiting at all.

Remember, Volvo fixed the rusty body panel issues in about 1993 by galvanizing both sides - no more rust! I have a 1996 850 that has lived in the rust belt and parked outside most of its life and in city parking - no body rust.

Take the T5M for a 30 minute test drive. Check the steering carefully. Make sure the heating controls work as new - set a temperature before starting the engine and see if the unit complies with the request. You should get heat within 1 mile.
Listen for noises in the front and rear. Ask for a scanner readout if you live in an inspection state, all 3 systems should be complete and no faults.

It's true... I would really like a T5M :>) just for the occasional times when I am at the head of the line at a traffic light. Perhaps, if a 2000 T5M comes my way...