Door Latch.

Hi im new to the forum, and since there is no Lexus threads, and since toyota makes Lexus, maybe I can still be helped, I recently bought my Lexus its a 91 ES250, and it has a few problems even though its still in excellent shape for a 15 yr old car, ok so one of the problems is that on the fron passanger side it cant be open from the inside, the previous owner said it had to do with the door latch and that she was able to fix it when it happened in the drivers side previously, (but for some reason didnt bother to fix it this time) so im not sure if I can actually fix this problem myself and how I can go about doing it, another problem it has is that the door lock doesnt work, im talking about the button on the drivers side that locks all the doors, it unlocks but doesnt lock, any help I can get would be greatly appreciated, thank you in advance.