I have an 04 GXP and the blower motor is surging from high to low when set to high. I know it is under the cabin filter, but how do you change it?

I changed my 2005 GXP motor. Go here for pictures:
https://www.gmforum.com/everything-electrical-electronic-108/2005-gxp-blower-motor-dead-277509/
The motor is pricey, but it doesn't take long.
Let us know if the 2004 looks the same as the 2005.

Luckily mine was changed long before I owned the car. Dec. 2006, mileage was 114,893 at a cost of $247 parts and $104 labor. I have all the service records from the previous owner.
Mike

wow $247, Luckily i get a pretty decent state discount at napa autoparts and the local GM dealership.. But thanks to ZeeVert for his how to, ill be saving the $104 if mine should ever decide to take a crap... (knock, knock on some wood) lol

Ordered a blower motor from Rockauto for $44 including shipping.

I don't remember any $44 blowers when I needed one! It sure looks like the right one.
But be careful, apparently there are a couple different blowers used on 00-05 Bonnevilles

Just installed it this evening. Exact match and only took about 30 minutes even after putting the tools up. The hardest part was moving all of the dang wires. Works fantastic! Local prices were $140 and the dealer was $210. I am ecstatic!

Zeevert - thanks for the pics!