I was working on my 99 Park Ave this weekend and I took the positive cable off the battery as a precaution to keep from shorting something out. When I put everyting back together Ii forgot I had the key in the 'on' position so I could turm the steering wheel. There was an arch and I heard the door buzzer going off. I didn't think much more of it until I started the car and noticed the gas gauge had jumped over the peg below the empty mark. That has happened before when i did some welding on the floor pan. Problem now is it stalling when coasting for an extended distance ( like a quarter mile). My question is could I have fried an electric component that would cause it to stall just by hooking up the battery with the key in th eon position?

Did the engine light or ALT light come on? I would start by having a good code scanner plugged into OBDII port and see if there is any stored codes. I would also have the battery load tested to ensure it is not a weak batt condition & or charging condition. Voltage from alt ok?
I always try to think about spark (or last connection) to ground. Sparking to pos can be ah not good. Check all your fuses!
If welding etc I would remove both batt cables but ensure if you have the stock radio, that you have the radio code set other wise it can lock itself down (theft prevention)
If it is stalling at idle see if the idle is suddenly dropping down or variable, wandering, that may be a hint of component damage.

I had a p1404 code yesterday ( Advanced read it for me but, would not clear it). Today I drove it 72 miles back and forth to work and it ran fine. The SES light did not come on at all today. Maybe it was just a fluke. Time will tell. It is a bit unnerving to think that you may be without power steering or power brakes at any time.

Here is a write up on P1404, but it probably is unrelated to your problem:

https://www.gmforum.com/obd-ii-trouble-shooting-153/p1404-284174/