You have some options, but depending on the option you choose, will determine the cost (if any). Hence...
1.) It has been talked about for years here, there is a way to bypass the amp completely. I'm not sure if you can do this with all Montes or not. Most people reported when doing this, the sound quality actually IMPROVED. Again, you'll have to research this. There used to be a "How to" on this on
www.impalahq.com but it seems that website has died.
2.) The part number you posted for your amp is $216.25 if you buy it from
www.gmpartsdirect.com3.) I also recall people talking about "103" amps and "104" amps years ago. Basically your amp is a "103" amp. (The part number starts with 103). Again, you'll have to research here, but I KINDA remember discussions where maybe a "104" amp MIGHT be able to be used in it's place, and IIRC, it was the superior amplifier. Can't remember if it was more powerful, or just seemed to be less likely to fail.
4.) If you want, I have the OEM amp I pulled from my 2002 Monte SS. It has model number: 10449234, which oddly enough is not a valid part number on
www.gmpartsdirect.com which is weird. I dunno. It has been sitting here in my closet for about 5-6 years and was functional when I removed it. I will sell it to you for $100 USD including shipping if you want, but I can't guarantee it is a direct replacement for your amp. If it doesn't work, I will let you return it to me and I will refund your money less shipping costs (and my paypal costs if we use Paypal.) I figure it could cost me $20ish to ship this to you if you're in the US, I am in Canada.
Good Luck!
Krunch