Diesel Bombers - 94 yukon diesel

hey so i picked up a 94 gmc yukon diesel from a guy that gave up on her, shes ok shape (other then acouple dents and i looks like its been a dog kennel for about 10 years) but anyways i need some help with the glow circuit does anyone know the ins and outs of it? when i got it he had the wires everywhere and told me it just needed a new relay because he could jump it and it started fine (bought a new one but the one in there was brand new and tested out fine) and the circuit running it seemed to test out fine too but now that i have it all back togeather and the batts went dead now it seems to not work no light on dash either so is there a relay that operates the other relay or straight off the key switch or etc

this is the first of many questions im more then likely going to have so any help is greatly appreciated and or wiring diagrams or pics or books you know with good info (that arent worth more then the truck ;-)