Thank you! =) I think it's perfectly possible, 1-2 evenings should be enough to build any one of the peripheral devices.
About the pot, something like this one will do: https://goo.gl/vbi1Zh , basically you need a linear pot, something like 5 to 10 kOhm that will fit the slot =)
About the direction of switches, basically in a real one (if we omit the fact that the governor switch is a 4-way switch), all switches except idle stop and starter go up-down. But I think its perfectly ok to turn them as you like ^_^