1992 Chevy Blazer Advice on repair of fuel lines

My 92 blazer was recently repaired after sitting for a couple years without maintenance. Worked great since for about three months when all of a sudden last week it wouldnt start. I took it to the local mechanic and he found that the fuel filter needed replacement. After alot of effort with old parts and dry rotted gas lines he managed to get the new fuel filter on. He told me that it ran shortly but wouldnt start a couple of minutes later. When I came in talk to him about the truck, his conclusion was to junk the truck due to its dry rotted lines and contaminated fuel (from sludge sitting in the tank and running the car low on gas) which was clogging the fuel filter. The main reason being that the cost to repair is probably more than what the car is worth.

One of the issues I have is if the cost is actually not worth it or not. Im assuming he saw the milage on the car at 170,000 miles but this is due to a new dash board.

Is a contaminated fuel tank with dry rotted lines an expensive fix? How much? And do you think that these two problems would be worth fixing if the car has under 80000 miles on it.

(does contaminated gas effect the cylinders or anything else that would do permenant damege)