I'm in Medford, if someone asked for a mechanic I would say Ken Scales; they are local to me, our company has had work done there, but they are a shop and going to be expensive (like every other place)
Me, I'd try it myself.
Like you said, a 90 degree drill. Get a set of left handed drill bits.
Get a can of PB blaster and squirt that broke bolt morning, noon and night, before and after every drive. Do that for days, let the heat cycles bust the corrosion loose and that PB work it's way into that thread.
Take off every part you can to reach it. Take lots of pictures. Have a clean and neat area to work.
Pulling the engine is a LOT of work, but you can do some amazing things with a floor jack under the engine and undoing the motor mounts. You can "float" the engine in the compartment, push it around with some 2x4 levers... might just get that extra inch to use the 90 degree drill.
Good Luck!!