It's been a while since I worked with the DK's and my manuals and half my memories are long gone, so I can't help a lot, but..
1) If you have the manuals and know how to program from a LCD phone, it is possible to find out the ROM version using either program 00 or 01 (I forget which one).
2) never dealt with a PRI, but I'm sure it will require a card in an expansion cabinet (which connects to the left of the main KSU), so if you don't have an expansion box, you may be better starting from scratch with a new KSU that will accept your current phone sets.
3) my programming requirements were simple enough that I did all programming from a phone set, but setting up a PRI might be better done thru DKadmin on a PC