Most bulbs are not a problem but some press switches can be more difficult. I suppose, if in doubt then don't, but I must have changed hundreds over the years without having a issue. Sometimes an engineer is not available - again how many times have I had to fix seats, top up oils and hydraulics, load bags, clean cabins - more times than I care to mention but sometimes you just have to get on with it..........actually, I can only remember a couple of times when I helped out with the baggage due to the Spanish being on strike !