Cooper S newbie - mechanical questions.

Hi all - Have a few questions for the experts here....

I am strongly considering buying myself a used Cooper S clubman but funding won't allow gong for the ones with the later (better ?) engine, so I'll probably end up with a pre - 2010 model.

I am a fairly enthusiastic DIY mechanic but never touched anything Mini before so are they a pain to work on or particularly better or worse than any other FWD car ?
Doing a bit of reading up online it seems that timing chain tensioners and carboned up intake valves are common issues - Anything else in the major mechanical department that I need to be paying attention to when I go out looking to buy ?

I hear the carboned up valve issue is down to the PCV valve and rocker cover design but there's a factory redesigned cover available ? Is there an easy way to spot if a car I'm looking at has already had the newer cover fitted - Are the modified ones visibly different from the outside ?

How easy is it to change the timing chain tensioner ? Engine out job or can it be done in-situ ?

Lastly (for now) - if the car does not have a DAB radio in it - how easy / costly is it to retrofit one ?

Dave.