Might appear pricey, but then a car overhaul will simply roll to a halt if it goes badly wrong, a single engined aircraft will not and on some twins if you lose an engine the other one will simply fly you to the crash site.
If you go for the likes of the engine in say a Beech Baron twin and for a new item you would be looking at the best part of £50,000 for one.
Most engines on I have had overhauled have new cylinder assemblies fitted as part of the job.
BTW the overhaul period on a 0-235 (dependant on pistons fitted) is 2400 plus up to a 20% extension ( Engineers Discretion) giving it a life of 2880 hrs... there is a new ruling now as well of a 12 year dependant on usage.
Good look with the flying, its always refreshing to find a pilot taking the time to find out more about the aircraft he flies.