Phil -
If you are buying the boat from a dealer, have them throw the '06 rudder in as part of the deal. The cost of the rudder itself is around $250. It takes about :30 minutes to install. I did mine myself. There is alot of info on the installation process over on the MasterCraft Owners site (
www.tmcowners.com) or on the Charlotte NC MC site (
www.mymastercraft.com). If you have to buy the rudder from a dealer, buy it from the Charlotte MC dealer. Ask for Mike McKenzie - great guy and probably the most informative person on MC boats I have ever met.
Regarding a sell price for the '05 - I think high $40Ks is good. You mentioned he is asked $49K or best offer. Offer him $45K and see what he says. You'll probably end of somewhere in the $47K-$48K range.