Need help with a wrenching failure

Tried to lubricate my rear sway bar bushings and had a pretty big failure. Backed the car onto ramps and then tried to do the job without dropping the exhaust at all. Required some awkward angles to get the bolts out, but I f’ed up and sheered the top left bolt right off as I took it out. I believe this is because I was using a massive extension and gave it an awkward twist. Anyways, now I’m stuck with 95% of the bolt still threaded into the car, with pretty much nothing exposed. Was too pissed/depressed at that point to take pictures :-\

Here is a pic I took when I installed my exhaust, you can see the upper right bolt holding in the EC sway bar

https://farm8.staticflickr.com/7291/12707564713_275f37e7d0_b.jpg

So my options now are to get a shop to do it or try myself. Shop will probably want $2-300, and I have to limp over there, hopefully not doing any damage (should be ok if I drive slowly?). A friend has agreed to help me take a look, and someone else is letting me borrow an electric impact and set of bolt extractors. I’ll probably go and grab a set of reverse threaded drill bits and broken screw extractors. But I don’t want to make it worse by doing something wrong. My buddy is pretty good with a wrench, but it’s always easier to work on someone else’s car ;D Would prefer to not use a torch or any other kind of heating, since that area is exposed to the elements.

Anyone got any advice, would much appreciate it!