Hi Jayslol. I'm in Canada as well.
Your friend will definitely still owe the difference on the truck loan if he were to sell it. I was shocked at the amount of people who didn't realize this is how it works. People would come to see me at the bank I worked for to pay off their car loan because they sold the car; however of course they sold the car for less than what they owed on the loan, leaving a balance owing to the bank.
Them: "What do you mean? I'm done with the car, I sold it! Why do I still owe you money???
Me: "Because you took out a loan for 15K, and paid us back 12,500 counting your payments and what you got for the car from the sale. Yo still owe us $2,500."
Them: "That isn't right! I want to speak with your manager!"
These were often people in their 40's. Imagine you could go and finance a new Beamer, sell it six months later for whatever amount, and the loan just disappears. That would be nice, wouldn't it?
Also I don't want to sound judgmental or harsh, but I'm quite certain your friend would not qualify for a line of credit (you normally need assets to get a LOC), or even a personal loan, at least from a bank. He has one bad credit sign from his missed truck payments, and that is likely not the only bad sign on his credit.
I would say the best option is to private sell the truck, and put that towards the truck loan, then suck up the balance with lower monthly payments.