Based on the information I saw on the Futaba narrow banding FAQ
http://www.futabarc.com/faq/service-faq.html#q41 it sounds like the transmitter and receiver are not narrow band. You may be able to find someone to convert the transmitter, but the receiver will always be wide band. I went through this same decision process last May. I decided that by the time I bought new batteries and sent the transmitter and receiver off to have the transmitter narrow banded and the receiver tuned, that it wasn't worth the money. I bought a Futaba 6EXA instead. I then bought a 4YF to give me a second flight pack, spare transmitter (which could be used as a buddy box), and transmitter battery. I'm really glad I went with the 6EXA, the computer features are far superior to a basic 4 channel.
When I ran out of S3004 servos I started changing the plugs on some old S38 and S48 servos. Buy some leads with the new style connector, cut off the old ones and solder the new leads on. So far, I'm only using these in a slow plane, Piper Cub. Works fine.