I would suggest the dealer as a last resort.
I recommend you go to the first mechanic. Why? You suggested you trusted him and he suggested you take your truck somewhere else because he was concerned he could not meet your needs . This shows intergarety, I would like to keep him in business. There is absolutely no doubt in my mind he can do the job, what ever it takes.
Do a search as I previously stated. I suggest you replace all tubing with a rubber hose, about 12 feet as I recall. Do not replace with factory parts.
If you print out the thread that explains replacing all lines with hose, your mechanic will understand. He will need a few tiewraps. Use the hose with the J30R7 or 30R7 marked on the hose. If he wants to do a deluxe job, tell him to due the flare trick on the line he cuts at the fuel tank end to assist the clamp in holding the hose on. If you use this method, the next time you replace these hoses (and you will), it will be a piece of cake.
Expect to pay for about two hours labor plus hose at . 60 to 1. 00 dollar per foot. There is higher quality hose available, but you will pay for it.
Wayne