Been there done that. First as you know removal of the brace is obvious. then pull-up on fuse box. More than likely your battery was replaced once before with the wrong size!! Many El-Cheap-O stores just don't know how to size not only the correct cranking amps but the size. I had the same issues, was sold one just the tinyest bit too big, but squeezed it in. On my next change I brought the Optima red top. The old one was a B@#$% to get out. The Optima was a prefect fit. On your ignition issue, you are part of the recall that GM has been doing. Bring it in for the recall,.

 

I got the new battery!! Unfortunately, the damned thing still won't start, nor recline.

As for the recall, I've tried that as well. They say that the fix is by getting new Keys and reprogramming or something. I asked if they replaced the Ignition Switch (Which the recall said was faulty) and they said No.

 

Alright I'm back guys!!!
Long story short, I've been paying Billions of dollars to tow the Car Back and Forth here and there.

I finally get it to the GM dealer, and something in the Shifting Mech. Failed. Like I said, I'm guessing a wire Popped.

$430 buck fix. Hopefully Maxcare covers it, so I can pay my $300 deductible and get back on the road before Christmas Break is over.

I've been car-less for just about 3 weeks now!

 

Also check the secondary ground it runs from your negative post to the car frame just by the battery. It bit me last year. The screw is in the painted part of the fram so the onnly grounding surface are the threads going into the frame. Mine was rusty (the threads) but you cant see them unless you remove the screw. This caused my 06 monte not to start, and locked the key into the ignition