"Really Difficult" would depend on your prev. experience level IMHO, it's a bit of a project if you haven't done anything similar before....
It doesn't sound good at this point, but don't borrow trouble yet B4 trying the hints given earlier!
Couple hints I thought of when reading this:
When you clean things up, use a light & peek at the threads to note any obvious damage that might be more apparent on 1 or 2 of them...
When threading plugs in, a piece of hose that fits on the insulator makes a good plug starter to run them in with by hand B4 torquing. That way there is no chance of damage from any cross threading (it replaces an "official" plug starting tool). You can also get a good "feel" this way of how solid the fit is between the plugs & the threaded hole. If they are in good shape you shouldn't feel a LOT of wiggle after they are threaded in most of the way. You'll ALWAYS feel a bit of wiggle when only a couple threads are engaged, and that should progressively disappear as they thread in further. If they still wiggle noticeably when they are almost seated it's a sign the threads in the head are worn & you should be very careful in tightening them.
The "tapered seat" plugs common now, as opposed to the type with crush gaskets, seat suddenly without much additional turning to achieve the proper torque value so more care is needed to get them tightened properly. Good excuse to get out the torque wrench over the "armstrong" finger feel method of determining the proper tightness!
Here's hoping that carbon buildup from loose plugs was the initial cause of your issue, and simply cleaning things up solves it!