While cboy is correct in his method of timing, keep in mind this is a computer controlled car. Some are very specific to the amount of vacuum (specially those run on a speed density type setup) they want at idle, and what base number the timing is set at. If Cadillac wants 10 degrees BTDC then thats what I'd give them. Once you have tore into the engine and changed parts and the computer for tha matter, its your own choice on what works best for timing. But with it as a stock application, you'll want stock timing settings.
I'd go with siggy's advice on timing for a fuelie, but when I timed mine i took the advice of a couple old gearheads I know, they said the book says 6 BTDC, run 10 you'll be able to hear when it's running better and sure enough they were right