Need a new diesel

Driving home the other night and it was really jumpy after 30 mins on motorway which it hadn't done before so pulled in at petrol station and bought some oil and noticed a **** tonne of sludge, got my mate to strip it once I managed to get it home and theres a crack in the block... No idea what caused it I dunno if these things just happen but I replaced my own head gasket so it was probably my cack hand which did it, but now need an engine

my mate said he can do basic things to it like replace gaskets piston rings etc but doesnt want to do a major overhaul, so does any one know where I can get a decent engine and how much will I be looking at to buy a decent 2.25 engine diesel for a series 2a

sorry this is a rushed one typing on me phone too

Any help will be great cheers

well probally ebay ????