Bryan, look at the mirror. There will be four little dots on it, two close together. two far apart. The dots that are far apart go to the bottom inside of the mechanical shelf that holds the mirror. There is a very thin plastic film piece that sits below the mirror. It has a very thin border at the bottom and is thicker at the top, with an odd shaped opening in the middle.
If the small plastic part is also falling out you will need to replace it first. Using a very small portion of thin two way tape, tape the plastic piece by putting tape on the bottom left and right sides of the plastic. Press it into place. The holder plate is recessed to accept the plastic piece, and it will sit for you. Now do the same thing with the mirror. Lay it down with the dots facing up. Using your fingernail, rub off any glue residue (the dots). Take two at tape and cut three small pieces. One will go on the upper part to cover both dots in the center (remember the dots are closer on top). Using one small part of each of the bottom sides, place the tape over the dot area. Nor flip the mirror over and place it in the holder with the tape facing down, and the long centered part to the top.
Its fixed. You need to clean the mirror by gently wiping it with an appropriate cloth. Blow and dust out of the cavity. You may need to adjust your eyepiece... Good luck.