That is a very good price. You got a lot of guts to buy a basket case for your first cycle. I always wonder why it is in boxes in the first place. My suggestions are to, Get a good manual, Take inventory Sportster Garage is a good one.
Thats very cheap price. The biggest pieces of advice I can share other than the basics of having good tools and a good manual are, BE PATIENT and BE THOROUGH! Try to enlist the help of someone who has done this before. It can be very intimidating if you try by yourself. Two heads are better than one for trouble-shooting electrical bugs so on.
You will also find that your local HD dealer will be of little help. They stock very few parts for your older bike. Try J&P Cycles, Nostalgia Cycle, and Texas Iron for parts. Hopefully your basket isn't missing too much!
I would definantly go to ebay to get anything that you need. I know that I have seen some of the older HD parts out there and that usually you can get things at fairly good prices. As far as your rebuild goes I would also suggest getting a checklist of parts made to see if you are missing anything before your start.