Shower head, fairly easy fix if you don’t have to replace the stem going into the wall. And, even that is not hard as long as the line feeding it is securely attached. Can be a bit of a bear if it is loose and you are trying to re-insert one of those angled pieces of pipe into it. If you are just replacing the head then no worries. Faucet could be a pain in the ass. What kind do you have single valve? or three handle? I ask because the three handle ones seem to be more of a pain than the single. If you have to change the entire faucet in the wall hire someone to do it who has the tools and knowledge. You can do it but you will not enjoy it and will in all likelyhood invent some new curse words. If you can get by with just replacing the valve that is great.Remove the old one and take it in with you to be certain of getting the correct replacement cartridge. Also, check the brand name, they will ask and it is important. For both all you need is a good Philips screwdriver and a couple of channel locks; although it wouldn’t hurt to have a pair of needle nose pliers handy to pull out recalcitrant parts.