We have twenty or so GU 10 downlights upstairs (lower ceilings as it is loft extension). Fitting LED in place of the Halogen is a straight lamp replacement, very easy.
When we had the down-lights installed we had a fire safety "sock" sort of thing fitted behind the lamp holders; I was told that was because the Halogen lamps produce so much heat - I don't think that this is the case with LED lamps.