I would also ensure that you get a decent warranty with the replacement engine, in case of sticking valves for example.
My 1.4 16V Clio suffered a complete engine collapse through overheating - water pump broke, cambelt snapped, big damage etc - and I had an identical spec'd engine fitted that had only done 55k miles, as opposed to 108k that broke.
Unfortunately it seems the 'new' engine suffered from misfiring, probably due to sticking valves and despite using fuel additives and fuel flushes, as well as initially replacing throttle position sensor &
pack in an attempt to solve it, its still not right and out of warranty.
Basically, common sense, make sure your replacement engine is working absolutely fine and ensure your warranty is good.