Huram
RE:stuck pins, Usually this is caused by dry lube or dirt in the retainer.
You might try a very small application of oil(a drop on the end of a toothpick) & then work the pin in & out. there is a spring behind them so it shouldn't be difficult.
The advance problem is also Probably dry lube, and needs to be serviced. There's a lever that's not free enough to work smoothly & is causing you're problem. Working the camera through several cycles may clean it up but I doubt it.