Harold and Gunner have pretty well covered all the bases, but please allow me to throw in my 2¢
I have a V-N #6 that came with a complete set of collets, but no end-mill holders. Seeing as how the 5V collets are rather scarce, I decided to limit my use of them as much as possible. So, I made my own end-mill holders. It's not that hard to do. I used ordinary cold-rolled steel and didn't bother with hardening them. They are accurate and are holding up very well.
I'm not sure how much Z-axis space you have on your #12, but if you don't have them, already, you might want to outfit yourself with screw machine length drill bits. I recently got US-made fractional, lettered, and numbered drills in one big index on sale from Enco for an affordable price.
I've found that my V-N doesn't like Albrecht chucks; they're too long and eat up too much space. So, I got a ball-bearing Jacobs; big mistake. It's huge. Finally, I got conventional Jacobs chucks. They eat up the least amount of Z-axis. A sensitive drilling attachment is almost a must, too. It's impossible to get much "feel" of cutting action when cranking up on that massive knee.
In case you didn't see my post of a few weeks back, I've put together a CD containing V-N #6 and #12 literature, such as catalogs, accessory catalogs, letters from V-N, blueprint of the cutterhead assembly (the #6 and #12 cutterheads are identical), etc. I make the collection available on a donation basis. That is, I mail the CD with the understanding that the recipient reimburses whatever amoun they feel like. BTW, R.C.M readers are to be commended for their generousity. I've concluded there are some mighty fine people in the r.c.m.world.
Orrin