Help! cummins swap info needed
 

Hey guys im new to this ive never had a forum account before but ive read a lot of them from here anyway my question:
I have a 1989 dodge w100 shortbed reg cab halfton im doing a cummins swap to and everything is almost done, all that is left is the new front leaf springs and the wiring and exhaust. My question is my mechanic doing the swap (im in college and dont have time) said that i need a first gen cummins dash and wiring harness so that all my lights and stuff will work and so they dont have to spend a lot of time splicing into my wiring harness to make it work.....i dont think it is a lot of work so what would it take to get all my stuff to work i dont wanna spend the $600 this guy wants for the dash and all the truck wiring so would it be easier to buy it all or just use my stuff? thanks all!!!