Charley,
For Question 1 & 5. I built a machine using some high quality drawer slides. You can see some pics in the members gallery. It works great, just not as durable as some other methods nor would it be suitable for doing metal or high precision work.
http://cnczone.com/gallery/showphoto...cat/500/page/1
As for the motor block. I did use them on mine to get as much thread in the usable area as I could but you can see that it wasn't necessary because the nut itself never comes that close to the limit. If yours happens to be the same I would think that you could omit it unless it serves some other function.
Marv