Pontiac: 87 gp serpentine belt, r s strauss, serpentine belt

Question
I bought an 87 gp 2 weeks ago it just started quealing under the hood. its been raining alot i thought it was the problem i let the car warm up longer thinking it would dry the belts out. didnt work i purchased a lubricant to spray on belts to stop squealing lol didnt work. purchased new serpentine belt after doing research figuring this the problem? im a single mom and cannot spend tons of money on repairs r&s strauss want 140+ for installation.. is there any way  i can install this myself? if so a few pointers would be helpful. i am handy with tools and have changed a starter and alternator b4 but with the instruction of someone.. any help is greatly appreciated.. sincerely Malena :)

Answer
Your problem may NOT be the belt but a problem with the IDLER PULLEY.

If you have tried spraying the belt with a SILICONE SPRAY solvent and it did not resolve the squeel, Spray the IDLER PULLEY TENSIONER BEARING.

Make SURE you make a hand drawing of the correct installation of how the belt goes around the various components BEFORE you remove it as you will NOT remember how to reinstall the new belt correctly.