Sounds a bit on the high side. Under $100 would be more reasonable ($80 more like it). Did they tell you that you've got a weak battery? I also have faith in you to DIY... if you're that worried about screwing something up, have a friend come over to help read OffroadX's instructions out loud while you do the work. You can do it...

CAUTION: This is a little lame, but somehow seems warranted... when loosening/tightening the battery terminal clamps, be careful not to allow the metal tool you'll be using (e.g., wrench) to touch the (2) battery posts at the same time... unless you want to see sparks.