Electrical Problem with my '04 GMC Sierra?

[RiverRunner]

Saturday morning, I go to crank my '04 GMC Sierra and the starter dragged/slow but started. Ran it down the road to the hardware store shut it off. Drug/slow again to start, went home and put battery on charger at 2amps for 6 hours(new battery 01/09). Had to wake up and drive 4 hours away Sunday morning at 4:00. Slowly crunk again, but got on the road anyway. I noticed that when I would hit the brake the lights would dim some or if I rolled down the window. Then notoiced the Voltage meter on the dash go up down erratically between 9-16 volts, one time the lights on the dash and head lights flashed. Then after another 30-40 mins of driving, it settled down just above the 14v on the gauge. IT stayed running until I got to my destination. Was there about 15 mins and was headed back home, it all started all over again. Although it was daylight now, the speakers would pop when i used the power window. Stopped at Orielys, they put it on there tester and they said it was a bad Diode in the Alternator. DId not want to pay $177 for new one, so limped on back home. Took the Alternator out and took it to a local rebuild shop Monday. He put it on his machine and said it tested fine, but it may be because it was cooled down. Said he could put new brushes and bearings in it for $50.

Went ahead and done that, just got home and put it in. The Voltage meter still jumps up and down, just not as bad.

I also noticed now that my AC only blows out of the DEFROST vents now. I hope I didn't fry anything in the electrical system!

Any ideas out there? By the way, I have already had the instrument panel/dash replaced under the recall, speedometer was acting up.

Please help....