For a definitive answer, the instructions are usually a good start, if none came with it,
http://www.dumasproducts.com/product_info.php?products_id=722 assuming its the Dumas kit.
For a boat that size, shape and performance, I would think a 3 or 4 blade prop about 35mm.
Prop shaft tube? Measure to where the motor is going, allow room for the coupling, that's how long.
Motor? 5 pole 385 or a 545 for a bit more go. Battery? No higher voltage that the motor rating.
Any marine 15A ESC, preferably not sourced from the orient via ebay. Marine because they usually reverse and dont do braking.
Radio? Nowadays, a simple 2.4GHz set would be the choice. No channel/crystal worries, receiver is easy to hide, no big long antenna on the TX.
Whether any of that lot is usable on another boat depends the next boat.