If it was me, id keep it, TBH its not rocket science to take a rsturbo engine out and replace it, can be done in a day, theres normally lots of engines about, if its just a case of a headgasket change, its a piece of piss, At least if u fix it, it will be done proberly, and give u that piece of mind,

if not u could buy another and had the same problem.

also nowadays, rst's have lots of miles on them and require a rebuild at some point, so bite the bullet rip the lump out, buy yourself a diesel for the winter, a build a good solid lump.