It really all depends how familar you are with HTML and what you're using to editing HTML with.
Personally, I use a text editor for HTML editing; edit+ [
link] to be exact. You can use notpad or any text editor you like. I simply copy and paste the code contained in the template into a blank document. From there I make the edits I need to make and then I copy and paste the revised code back into the template and save it.
Regarding the template guide, Jelsoft does have one, but I don't know how helpful it will be. Look in the members section of
vBulletin.com.