Any tips on how to trouble shoot my oil pressure gage on my 1989 Camaro RS 305 5.0L engine. It working before untile I was missing with the dash pannel and didnt disconnect the battery when trying to intall oil pressure gage back to its position when a spark and smoke appear.

There is a reason why you disconnect the batt when playing with the electrics
A small short can zap you computer.
In your case you may have blown the gauge , disconnect the wire at the OP sender on the engine and touch it to ground it to see if gauge needle moves

Ok I purchase a oil pressure switch and replace it and the gagae still dosent read when you idle give move oil pressure I do notic when I start the car gage jumps and slowly drops were it stays what now?

You will probably have to go to the bone yard and get a different gauge.