I used a special extra long 10mm box wrench to do mine, the regular 5" long 10mm I had wouldnt move the bolt. I got it from sears, was 15$ i think, its about 8-9" long.
If you're having starter problems, first thing to check would be the contacts. These are very well made starters, the only real wear point is the contacts, which can be had for less than 35$. much cheaper than a whole new starter. Just did mine a few months back, I got a lot of clicking, then it would start. The contacts were well cooked. Whole job took about 1. 5hrs. .
good luck
-j