I think Fatar manufactures keybeds and keyboard parts.. then there are a number of other MIDI-related companies such as Doepfer. As for modwheels and pitch bends they are just potentiometers at their core, there's a store called keyboardparts or something so you could check their catalog or Google around.
As for MIDI stuff I have an Arduino Uno and a protoboard but I'm still a noob at programming and electronics. Basically you need sufficient I/O depending on your needs and some C code or similar to program the FPGA, and connectivity (USB etc)
So far the Uno's don't have native USB-MIDI which means you'll need 3rd party software such as loopmidi and a serial-to-MIDI converter, the MIDI libraries are free under the GPL ie. open source and available to all.