so. 22 pistols. there are many. many of them are "not bad". 22s were figured out a long time ago.
"can't go wrong with a Ruger Mark I/II" imho. i don't like the Mark III - too many fiddling safety pieces. bah. keep it simple.
difficulty. they're really simple to assemble and disassemble. READ THE MANUAL. there are some videos which show you how. if an 8 yo can master it, you can
tip: use a 9mm or so bullet case to pull that frakking lever up. or use a piece of nylon line or even a paper clip. anything but your thumbnail.
assembly: follow the directions. my dad couldn't, so i, a that 8 yo, ended up cleaning the damn thing. which is good, as i still have that gun. the manual is online if you don't have one.
though, these days, there are many very good choices in 22 pistols.
i like the old high standards. you can find them a lot of places. better than Buckmarks imho. also better than the S&W model 41 which have a stupid spring that sometimes fails, but also, cheap, so... the high standard super trophymatic is actually 8 ounces heavier than a typical 1911 pistol

talk about stable platform.
sig mosquito - avoid
sig trailside though? that's a rebadged hammerli - that's badass. i LOVE the hammerli ipsc 22 target pistol. accurate as *hell*. wow.
the newish Ruger SR 22 iirc is a good look semi-auto for many purposes. don't have one, but i'm thinking about it "down the road" (esp used).
for training, newbies, you want something easy, light, and friendly. a 7 shot revolver, where you can control how many rounds, and how many dummies, makes a GOOD choice for folx learning to not flinch, and hold rock steady. some of them also can shoot .22 WMR for fun
one of the reasons revolvers tend to be very accurate - no moving parts in the barrel line - it's integral to the frame. unlike say, glocks, and such where everything is jiggity. same reasoning behind target 22s. the barrel is typically monolithic to the frame as well. the SLIDE moves, and so do the rounds into chamber, but nothing else. again, compare to a glock. gah. it's wonder they work (they do, but still).
accuracy. with the right gun, and right round, SMALL groups at 50 yds is quite doable. if you can teach that, you can then learn anything else with confidence
imho