Is that because these overheat?
Is this a relatively simple task? Or is their a lot to consider compatibility and fitting wise?
Not entirely - All that rubbish will make it difficult to get the fitting out and it will tumble down through the hole.
The swap to GU10 simply means that rather than the mains cable going to the 'transformer' then on to the 12v light, the mains cable goes direct to the GU10 fitting.