Am i biting off more then i can chew with this new mustang project?
you can do it! I got a 1965 mustang when I was 15. I'm now 22, and I've done a little body work, put seat belts in it, rebuilt the motor myself, put a late-model Tremec trans in it, put a narrowed 1968 9-inch rearend under it, installed my own stereo system w/ hidden cd changer, put disc brakes on the front, and numerous other little stuff. Don't be intimidated, old cars are very intuitive, which means that the way they worked makes simple sense. One thing I loved about rebuilding my motor was that I could climb up in the engine bay of my Mustang and root around in it. Can't do that with many modern cars!
I did have the benefit of being good friends with a guy who's been a mechanic for about 25 years, and this helped greatly. although all the actual work was done by myself, my girlfriend, and my dad, having someone very knowledgeable just to ask was a big help. I've used a Chilton's book for a lot of stuff, too.
There's not really an estimate on how much it will cost to get your Mustang the way you want. Mine's had a few thousand $ dropped in it and it's still a long way from perfect. BUT, with a 1972 302 with a 4- barrel Holley, it moves me down the interstate at 23mpg, and will hang with the new Mustang GT's.