Help with building a controller board

I am looking to build a piggy back controller for an automotive application to help drive the transmission and also apply exhaust brake. I am completely stupid when it comes to actually selecting the parts and probably just as dumb when programming comes in. Basically what i want is a device that will turn on and off a device when the voltages are within parameters. Input would be Boost (variable voltage) Throttle position (variable) speed (pulse voltage, pulses/sec) brake applied (on off volts). outputs would be TCC locked/ unlocked and ex brake on/off with possibility of number of cyls to be applied. I'm sure I'm not including all of the info needed but hopefully this will get me started. I know I could probably just buy a pre-made controller but I enjoy the unlimited ideas you guys have on here. Also the more I can learn the better I can make it. Thanks for any help