Cadillac Repair: 85 Cadillac Fleetwood Service Engine Light Soon/Gas Guage, cadillac fleetwood, volt ohm meter

Question
Okay, I just bought an 85 Cadillac Fleetwood today. She only has a little over 49,000 miles. She also has a new air filter, battery, water pump and fuel pump. There are no leaks, however the 'Service Engine Soon' light will not go off. In addition, the fuel gauge does not appear to work. When I bought the car it read 4 gallons of gas, and the 'fuel used' works fine. However, after putting in 10 gallons of gas and driving for nearly an hour the gauge had only lowered, never registering the new gas put in. I have tried changing the fuse, because the service a/c light was on as well. Also, several times now while backing the car up (not touching gas or break) the car has simply died. Once while backing up alone, and also while switching from reverse to drive (I did have the break down).The radio also seems to have a few issues, randomly blaring while the volume has not been touched and sometimes completely shutting off. Can anybody offer some imput on any of these issues? The radio isn't really a main concern, but if it could be fixed it would be nice.

Answer
If you are mechanicaly inclined or know of someone who is, You will need a DIGITAL VOLT/OHM METER, Simple electrical schematics, Test procedures and picture locations of the components within the system that is causing you problems of which can't be done on this website which only allows one picture. I do not have a website so you will have to

e-mail: onlineautohelp@msn.com

in order to obtain the information necessary to fix your vehicle.