Start by checking and cleaning every ground front to back and top to bottom. Its free and easy and resolves many issues.
If you decide to rewire..
An original harness can be cost prohibitive as you have to purchase several different component harnesses. Both Painless and American Autowire both make somewhat application specific harnesses. They differ from factory in wire colors, connectors, etc. Both are roughly $750 for the complete harnesses and I have used coupons in the past with different sites from 10-20% off that price. Additionally, you will need to buy Packard Crimpers for the AAW kit, not sure the connectors on Painless, which are just under $200 for the pair to really do it right. I also have purchased additional packard connectors online for around $50 to tie in accessories.
It's not hard to do yourself if you buy the correct tools/ accessories and really not even that time consuming. If you don't buy the correct stuff, you'll be frustrated, annoyed and it will feel overwhelming. If its a custom truck, the challenges are aftermarket accessories, custom routing etc.