My first hand gun is a Ruger Mark III target pistol. It's accurate, cheap, and fun to shoot. But it is really, really hard to disassemble, clean and reassemble. 22 long rifle is a very dirty ammo. I feel no choice but to completely clean it every time I shoot it.
The first time I disassembled this gun, it took me more than four hours to put it back. I had way overestimated my mechanic skill and ended up going to bed 4am in the morning. The major trick is the position of its hammer. Now here's a video on youtube that explains this trick very well.