Cadillac Repair: 1996 CADILLAC, cadillac sedan deville, best bet

Question
I have a 1996 Cadillac Sedan Deville.  I am having some kind of electrical problem where my all my check engine gages come on.  The anit-lock brake, over heating, you name it it comes on.  Also when i am driving my speed goes up and down consistently while my miles rack up non-stop even when stopped at a light.  The light where it shows me what gear I am in flashes and that is when everything goes crazy.  I am not to sure what is making this happen but I need some help.  The dealership told me it was a 80% chance it was my battery cable but they wanted to charge me $800 to fix it.  what else might it be so that I just don't give money to the dealership and still not have it fixed???

Answer
I have NEVER heard of this problem before, but my diagnosis is somewhere in the dash connection, sorry i cant pinpoint this, consider replacing the fuse for the dash, checking the grounds which is always a possibility, unplug the battery for over an hour. Its most likely the dash itself has malfunctioned, your best bet is to take it to the dealer and have them diagnose it.