Gary,
While I can appreciate your optimism, I really do not think it is that easy. Besides the back, you will need to purchase a back adapter to fit your camera body and they can cost in upwards of $1,000; and then there may be some cables and batteries necessary. Try calling the dealers posted on this site to see their offerings. I did what you are trying to do in 12/2009. I purchased a used P45 from Capture Integration and when it was all said and done, I paid $12,000 for the back, $530 for 2 sets of cables, and $1695.00 for a used sliding back totaling, $14,225.00 + tax, etc. Expensive! (I went back and checked the invoice for specifics).