The coils on the indoor part of our air-conditioning/heat-pump system are dirty. Is this something I should try myself? I'm any sort of professional. Some sites say I could do it myself, some say it should be left to experts.
I usually use a pump up sprayer with some coil cleaner. You will be just fine with just plain water. If you don't have a pump sprayer you can use the garden hose just dont hit it with a lot of water. You don't want to get the blower or anything else wet. Also make sure your condensate drain does not plug up with the crud.
This is an inside evaporator guys, not the outside condenser. A garden house will create a wet mess.
Most manufacturer's will tell you what type of brush to use to clean the coils dry. If you can't locate the manual that came with the unit then Google "condenser brush" and looking at your unit and accessibility figure out which type will work best for you. Keep the shop vac going to catch the dust because it's very fine and irritating.
Yes I meant garden hose, not house. A garden hose would create quite a mess inside a residential house, but would probably be manageable inside a garden house. Although I have yet to see a garden house with AC.