OK, Progress
So it looks like it is a NavAll 3. Probably someone over here should have the firmware. I can't find any post that links to a download location of the firmware unfortunately.I would suggest asking in the general forum for a better chance of success.
A factory reset can't do any harm regarding the condition the unit is in now. It will however probably only help for a short amount of time because the flash memory might get wiped but the programs and firmware basically remain unchanged :|
You might consider retiring the unit and get a new one. Because the NavAlls are (to say the least) not very good and reliable. xTrons are pretty good in my experience or you could go for a generic 2Din with an accompanying frame.