Jump in feet first I say !!
Well not really, but I took pot luck when I bought my 230sl on ebay from a dealer in VA.
I'm still finding out "interesting" things, for example last week I started to dismantle the engine from the bottom up (it's out of the car)
I knew it needed new crank shaft seals, but was hoping the top end was ok. Not to be, when I took the valve cover off, the engine was horizontal on a stand, something fell out on the floor, it turned out to be a valve collet. But on checking to see which one I was surprised to find them all in place, so clearly whoever worked on the engine last must have dropped one, not finding it went on to fit a spare I assume, just very lucky that it didn't find it's way into the timing chain.
Before this, when I removed the petrol (gas to those in US) tank and the level gauge sender unit, there was a "tide mark" which indicated that the car had sat around for a very long time at some period not so long ago.
Back to the engine, because the car had not been driven or even started apparently, there are stain marks and cavitation present in the cylinder bores. On measuring the bores we found that they are standard as is the crank, and even though the car had good oil pressure, there is damage to the bearing shells mostly due to the car apparently sitting around for many years.
I'm now looking for new pistons, main and rod bearings.
Oh ! I forgot to mention, the head has been welded at some point, is warped and soft, so also looking for a new head !!
The cam shaft was trying to run following the curve in the head, so the centre bearing had picked up as well.
Just a thought, but if a car has relatively low mileage, but has sat around for decades with out a regular oil change and turn over.. beware.
Jack