The 0-300 engine is a peach really.Smooth and nice-sounding.
Contyplodicus engines are better for low utilisation aircraft when compared to Lycosaurus because the cams are on the bottom of the engine sitting in the oil. Low utilisation Lycos from experience are prone to corrosion on the cams and followers. Once the surfaces corrode too far the degeneration is a bit rapid.
My old H model was just lovely but my favourite model with the leading edge cuff is the M model, slightly faster and sweeter handling.
Recently flew a 172 H fitted with a diesel engine and it was sweet as!
0-300 powered 172's are cheap to buy and run so go for it, you will all fill your boots with flying experiences. Good luck.
SB