mine did that too. looks like you are going through all problems i had with my car, one at the time
i believe it is the same with other old micras
the job itself is pretty easy.. you will need big flat screwdriver/metal rod and a hammer.. also pliers for removing small locks at the end of the pin - i dont know the exact name
each door has two hinges and one thingie between them - it locks open doors in few positions.. first you have to hammer out the small pin holding the middle thingie in place.. it is removed from top, so hit it gently from the bottom
then support the door from the bottom on both ends.. also prepare something from the outside of the door to support them.. for example a chair with something heavy on it.
remove aforementioned locks on pins and then gently with a help of screwdirver/rod hammer them out.. "big problem, big hammer" maybe you will have to adjust the supports to make it come out easier..
remove the door.. next step is checking, if the pins are worn heavily.. if not, your problem is in the "rings" sitting in hinges. you can hammer them out too.. good thing is that they are much easier to manufacture..
if you cant get a hold of new pins, it is possible to insert some kind of thin metal spacer between the two parts of the hinges.. of course, only as a temporary solution.
hope you understood
it must be like listening to Vietnamese sellers trying to speak Slovak here