Hi, (BTW we use our real names on this forum. Please read Forum Rules)
Welcome to the forum!
For a major job like this (sounds like you want a total rebuild), I would have this done by someone like J-Corder.
And unless there is some particular reason you need the extra features on the 1520, you may want to see if Jeff will just take your machine and sell you a 1506 which has the head configuration you've chosen. It would just need the Bottlehead kit installed.
The main advantage of getting a J-Corder machine is
everything has been rebuilt so you'd be getting one that's better than new.
http://www.j-corder.com/