Well, I'm not sure yet about the size -- depends on how much you're putting in; I could make it a neat-looking, coffee-table size book in 8.5 x 11 if you give me enough pages.
The format will probably be in Adobe InDesign (my son got it at discount and is giving it to me for an early B'Day present.) I'm going to be learning it in the next few weeks, and will be using it for the cookbook anyway. Right now, Word is doing a great job on your book.
Oh. I assumed you already had a size in mind, and by format, I was referring to image file format. Should have been clearer. As I already said, size, format, layout, etc. is up to you. I figured the least I could give you for your hard work was artistic freedom.

Go nuts.
The reason I need to know (there's no hurry) is that the lady who did the cover art needs to know what file type and resolution she needs to send me. That's all.
What "bits and pieces" are you talking about? If you mean the "unfinished" stuff (do you still want those left out?), it should hardly be called "Errata" -- more like... "To Be Continued". If you're talking about some other bits we haven't seen yet, that's different. There's no problem with a separate section -- I had that for the Unfinished stories anyway; I can change the name to suit.
Even though it will knock the size down, I think the unfinished stories should stay out. I think they'll annoy the reader. (Sure got me lots of annoyed emails on the 'net. ;P).
I could start a poll, though. Since the people most likely to buy this thing are TCF members, a poll would show if said readers feel the same way.
By errata I mean bits and pieces that I've saved from various forums over the years, like the "Frontierism" piece, and a few flash fiction stories from a weird collaborative writing thread on ASC called 2064. Couple rants like 'The Last Argument Of Kings'. Stuff like that.
If you're going to have notes, I need to know how long they'll be, and after which pieces.
I had in mind a couple pages at the very end.
One suggestion, if I may: don't write too much; the charm and impact of your stories are better left unexplained. Fiction especially is better left to the imagination; and the non-fiction, too, is nobody's business but your own.
I don't think I could explain my stories if I tried. I meant more like "This story was inspired by..." or my own opinion of how well it worked. And by brief I mean
brief, like 30-50 words each. For the non-fiction, it was actually the first stuff I ever sat down and wrote for an audience, and I'd like to talk a bit about how that felt. Most of the poetry is from my tradition of writing a Memorial Day poem, and I'd like to mention that.