I'de say you probably wouldn't come out with too much difference cash wise for the first build, and if you're only doing one build, pay a pro. Personally I took the plan 'B' approach and spent the cash on some good tools and hunted around for suppliers of quality parts and a good machine shop. Don't scrimp, pay good money for good work and most guys will be prepared to share the knowledge.
If you take the DIY route find a good mentor, it'll save loads of time and ensure you do it right. At the end of it you will;
a) Be more confident with spanners
b) Have a great toolkit of quality tools that should last a lifetime
c) Save $$$$ on the next build/rebuild
d) Understand your motor better
e) Have a massive sense of pride in your project
f) Be more game to push the modification boundaries in getting more hp/performance out of the car
Take a look at 'Sterling's' project. I take my hat of the the guy. Some of the stuff he's done isn't my cup of tea but what blows me away is his approach. He seems to be doing most of himself and is turning out great results. Occasionally going a couple of steps backwards but most of the time running forward. Its kinda like a DIY apprenticeship. Can't wait to see his next project.
My first build was a stock 2L that I blew up within 500k, I took it apart with a couple of good mechanics and learen't loads about what I did right/wrong. Now I'm proud to say my little Kent, that I build from the ground up myself is a little ripper that generates enough hp to put a massive smile on my face. It hasn't been a short learning path but certainly well worth it.
If you don't enjoy tinkering or have the patience to do/redo a job a few times before you get it right, this might not be the right way to go for you.
Cheers,
Mark