Not sure about the s100 specifically, but I've converted several plastic kits to R/c, (Corvette, Enterprise, Linberg Blue devil etc).
The scale prop size for these kits is probably a M2 or 2mm size, I buy them from "Model Boat bits,
http://www.modelboatbits.com/. The owner, Steve Tranter is always very helpful and will produce things to order if not correct, (he built me a brass Corvette rudder to replicate the plastic one supplied with the kit.) He also has suitable "A" and "P" frames.
He also stocks the superb Raboesch Props, which although not cheap are superb.
With reference to motors it really depends how many you want to fit!. I have seen this boat built with one, two or three motors, so the choice really is yours....I think I would build it with one decent spec motor as there is not a great deal ofroom available....
The rest of the components I guess you can source locally or if you want to use Action bits direct from their website.
Hope this is useful.
Regards
Alan