Sort of late the party here, but I pretty much did the exact same thing. It took a little bit of extra time on the first side (started with passenger) to work out what was the minimal amount of work needed just for access, but the second side took less than half the time.

Also, I picked up a ball joint separator from a local parts store, but it wasn't large enough. So... I ended up using my 27mm wrench as a you would a pickle fork and put pressure on the old arm while giving the ball joint a couple of good smacks with a hammer and it popped right out.

Those plastic rivets are pretty cheap. When I replaced all of the engine partition, I bought a bunch of extra ones and paid less than $1 per rivet. Well worth it since there are so many and many I've found all over the vehicle are worn out or simply missing. I did find one during this work that didn't appear to actually connect to anything. (stuck in the liner through a hole that appears to have been connected to some other part in the past. )