Hi Joe,
If you haven't seen it, have a look at my thread I posted about a year ago about the body I built for my Ragleth :
http://gardenrails.myfreeforum.org/ftop ... -asc-0.php
This was my first and, as yet, only attempt at building a brass loco body and I found it quite straightforward and enjoyable. A bit of experience in metalwork would be useful - mine all came from restoring cars - but as long as you have some aptitude it's not difficult.
You only need basic hand tools, hacksaw, drills, hammer, a selection of files - you'll do a lot of filing ! I have a pillar drill which makes life easier but you could manage without. The only other essential is a decent vice. I also have a couple of lengths of angle iron with a nice sharp angle which I can put in the jaws for bending the brass.
Make your body out of cardboard first - you'll probably make two or three before you're happy with how it looks, then transfer it to the metal. If you're intending to fit radio control, bear in mind how you're going to fit it right from the start, or you'll end up with a space that's a millimetre too small for what you want to put in there !
I used 0.7mm brass which I found produced a nice solid body but is still easy to cut and bend. As for soldering, I never found I could get enough heat from a soldering iron and ended up using a miniature gas fired blowtorch which worked a treat. Again, soldering is not difficult but needs a bit of practice if you've not done much before. And it's a lot easier with proper lead/tin solder rather than the awful modern lead free stuff.
Hope that's of some assistance,
Brian