No, I dont think you need a new cooler.
It will cost you a couple of hundred dollars to try to restore the cooler.
But I do believe there is a way. I have done it on mine with great success.
1 pump from northern tool - Portable Transfer Pump — 115 Volt, 5/8in., Model# 50AC110B | Utility Pumps| Northern Tool + Equipment
Or similar pump.
About 15 to 20 feet of 3/4 x 1/2 clear vinyl tubing
Enough fittings to connect 2 garden hose fitting to the hose.
One 3/4 ball valve a kc nipple and a couple of close 3/4 nipples.
The one pictured is steel, but are available in plastic.
About 10 to 15 feet of 1/2 x 3/8 clear tubing.
2 clean 5 gallon buckets ( optional to have 1 plastic and one metal)
1 small kiddy wading pool.
Optional heating element to heat the chemical you are using.
A couple of rolls of the blue shop towels on a roll, and a large funnel.
Start by pressure washing the underside of your vehicle around the front cover and the steering stabilize and crossmember. Squeaky clean.
First place some of the blue shop towels around the outlet port of Oil Cooler so that if you do drop anything it will not get lost in the valley.
Remove the outlet port of the oil cooler that is under the turbo. Most will tell you you will Need to build a special tool to get two the torx headed bolts but I have found you don't.
Take a 1/4 inch socket set with about 10 inches of extensions and one swivel joint on the very end and place a 1/4 socket on the end of it. Find the appropriate torx bit to fit the screws in the cap. To hold the torx bit into the socket insert a piece of the blue towel into the socket along with the bit, making sure it gets on the sides of the tork bit.
Place about 10 feet of 3/4 x 1/2 hose into the outlet port of the oil cooler it will it snugly in the port. The other end will have one of the KC nipple in the other end of the hose with a 3/4 in ball vale on it and an adapter to hook it to a water hose.
Next drain the anti freeze out at the drain on the bottom of the radiator into one of the 5 gallon buckets for reuse later.
Next remove the shrouds from around the fan, then remove the fan, fan pulley and the water pump.
You will notice various passages inside the front cover for coolant flow. Plug the bottom passage and the big hole in the center of the front cover where the pump when.
Place the kiddy wading pool under the truck to catch the water from the dedicated passage to the oil collier that will exit at the top of the big hole were the water pump went and run down into the kiddy pool. If you got the under carriage clean enough the kiddy pool will catch the contaminants from the oil cooler and you will be able to see some of crud that comes out of the cooler when it it flushed with plain water. Kink the hose or turn the valve off and on to create a surge pressure to dislodge more debris.
I did mine for about 2 hours off and on before I was satisfied I wasn't going to get anymore out by that method.
I'll finish this in the morning.... Nite nite