91 Buick Skylark Custom

I Just got the car 2 months ago its a great car but it needs some fixin up. so far there are only two things wrong with it: 1. when at a complete stop if i floor it it acts like its about to die but will get going a friend told me ive got clogged headers but i wanted to see what you guys think and if you guys know how to fix it. 2. the rear axle is rusted through on the passenger side and its gotten worse over the past couple weeks. ive looked online but havent been able to find one anywhere i was wondering if any of you knew a website to order a new one off of or if you knew anybody who was looking to sell the whole car even if its kinda beat up but its gotta be cheap