Wolf these guys gave you some great information,
1st thing I suggest is , if the screws are missing and the seal was broken, then good chance they have changed the dvd drive and no longer have the proper dvd key that goes with your mobo.
2nd thing , to stop the over heating issue you could take it apart, I would check the board over to see if its warped, if its not warped and want some help I can guide you along with the re-flow proccess, and you want to get some artic silver 5 paste, you dont need alot but it can make a difference if you use the wrong stuff or put too much AS5 on it.
3rd once you solved the over heatting problem at least you can use it for a good dvd player if you wish. being it doesnt play games there isnt much you can do at this time to fix that. let me or someone else know what you want to do. before going anyfuther.
Feel Free to PM me.
Rodent(Local Moderator)