I agree that one should know how to change the engine oil, and the gear oil if appropriate, however when i try to get the filter off, I sometimes end up having to find someone with more strength, ( I do have a patent gadget, but it does not always co operate). I like to have the gear fluid changed annually, but I can't reach it, in fact I think only one bod (out of four), has ever removed the magnetic sump plug.
I have come to the conclusion that once I've found a good engineer, I should get the work done, no matter that it costs a bit, it means I can phone him if something goes wrong, and hopefully he will come and sort it, a bit like having an RCR contract, just cheaper!