Electrical prob

I have a 98 gt 187,xxx on it today driving home from work the radio shut off and the check gauges light came on the HUD and looked down and the battery light was on and losing battery power fast so i pulled over and took the battery and Alt in to get tested they both tested fine started it up and ran great then it started running funny then lights came on again and it died and now it wont start tried jumpers they did not help. Cleaned the battery terminals but nothing helped. There was a good size spark every time you disconnect the battery.

PS the SES light is always on do to the rear O2 sensor so dont know if that would of turned on to at that point. Should i go to the dealership to get it fixed if i cant figure it out in the AM I live just north of the twin cities in MN
Any help would be greatly appreciated

your symptoms indicate a possible bad ignition switch/harness, a common problem on these cars with high mileage. The terminals where the switch/harness connect to the vehicle harness get weak with age and start arcing, causing all sorts of electrical gremlins including everything you described.

It ended up being one of the posts on the starter was messed up and shorting out and sucking all of the power out of the the battery.

My wipers started to stick up again and went to fix them and realized that the wiper clutch or trans what ever it is called had a metal tab broken off and it wont work right called the auto parts store they said that is a dealer only part is that true?

if it's the tab on the mounting bracket that the wiper arm strikes to park, then yes, that mounting bracket is dealer only. It's called the windshield wiper support, and is GM part# 12368639. Dealer retail is $247, and it fits all GP's from 97-03 if you want to go boneyard hunting due to it being so expensive.