If by speed control, you mean cruise control, ie, the ability to maintain a constant speed around curves and up/down grades, here's what you need:
-a can motor from Timko repair depot, or one of the other vendors that make can motor conversions for Flyer S gauge steam locos
-a cruise Commander from Electric Railroad Company
If by speed control you mean just being able to run the loco with TMCC, then all you need is
-an AC Commander from Electric Railroad.
Installation is fairly straightforward, but if this loco has a metal tender, you will have to figure out a suitable antenna. Carl Tuveson could answer your questions better than I.
http://www.tuveson.com/
http://www.electricrr.com/
http://timkorepairdepot.com/Services.html