Hi John,
I would look for a compatible Bigsby tremelo system, I am not sure which model will be compatible with the ES-1G.
As for pickups what style of music do you like playing ? Some humbuckers are more suited to rock or blues or jazz styles.

As for the electrics I would order mini pots will be much easier to get through the F holes. Get a decent 3 way switch and jack. Capacitors will depend on what style of music you will be playing and your preference of tone