I'm in the process of building it starting from a unserviced kit from LMI, which means starting from scratch but with all the materials avalaible.
Here is the story.
I started Easter day this year and i'm almost done, hopefully by Christmas my beauty will be ready, although after a couple of months i was working by myself (following the cumpiano book and a nice DVD that came with the kit from Robbie O'Brian) I stopped because I made a MAJOR mistake on the top of the guitar while inlaying the rosette channel.
That bummed me out and I didn't feel to continue 'cause even if i finished with no other problems, that mistake was there right on the top.
I started again about a month ago because I met a luthier that lives about 10 miles from where I am.
When I went to the shop I had in mind to ask him to finish it for me, but I dared and asked him if he would coach me so I could finish it myself, I was ready to ask how much for it, and he actually asked only to "Help him to keep the shop clean".
I couldnt believe my luck, I got a "wax on wax off" kind of deal!!
Working with a luthier made everything easier of course. having knowledge and a shop full of tools available it's priceless.
that said I still think it's possible to finish a guitar by yourself and without all of the expensive tools, before i made the mistake I was doing pretty good while having a great time. And even after i made the mistake I could have just bought material for another top and go on with my project.
Granted, you are going to need some tools but you can buy them one at a time when you need it, and you are going to make mistake that are gonna cost you time and money
Regarding knowledge, well this is the internet age and you can find pretty much anything you want. here is a couple of links that should get you started:
So my advice is do it without setting your goals and expectation too high, at least for the first guitar!
Keep us posted, I'll try to do the same