Welcome to the group.

I'd check the idler arm bushings, and the ball joints first. They wear and will give inconsistant wobble.
Stock Mitsu steel rims are VERY tough, and won't bend easy. A bent rim WILL wobble consistantly. Did they check the balance, or just take a guess?

Tires with rims, mounted and balanced: DiscountDirect.com is your friend. For slightly less than the price you mentioned, I recently got Nitto AT's 34x11.5's on 16x8 aluminum rims mounted, balanced, and a set of locking nuts, delivered to Bellingham. What you want should be a whole lot cheaper.

Good luck!