john deere 700

My JD 770 was running but died due to broken wire in seat switch now. I replaced seat switch and now I can not get the engine to even turn over. Lights come on, on the dash but no fuel relay click or any other sound. Lights on dash dim when I try to turn over engine but nothing happens...

Hey I've been grinding corn with my jd 700 grinder/mixer. However has a 1000 pto. I'm wanting to change it over to a 540 pto. That way I can use my smaller more fuel efficient tractor. What all would this require changing? I'm sure it will require changing the gearbox, but what about anything...