How handy are you? I did mine myself.
New turbo at 88K, maybe but that doesn't seem likely. If you have the work done, any reputable mechanic will service (clean the vanes) on your turbo and inspect it while it's off. It needs to come off for the oil cooler.
These trucks have some inherent problems, the oil cooler is one of them. If you decide to do the work or get it done, make sure you flush your coolant system first with Restore and Restore Plus (described in detail on the forum). Install a coolant filter and run it for hundreds of miles before changing the oil cooler (change out the filter at least three times during these hundreds of miles) to catch all the crap broken loose during the flush. That filter (and your clogged oil cooler) should capture most of what broken loose from your flush. Skipping this step will likely result in your new cooler clogging to some degree with the residual crap in your system.
Your problem was probably started by poor intervals on coolant flushes and the use of Ford Gold coolant. Change your coolant to CAT ELC-1 and you should have better luck!
Depending on where you live and the smog regulations you can either delete your EGR cooler or install one made by Bulletproof. Their design is better and it will not (should not) clog up. You have to pull the intake and EGR cooler to get at the oil cooler, and the EGR cooler is a known weakness in this truck. Skipping this step would be a mistake.
Cleaning the EGR valve is a simple job for anyone with the slightest mechanical ability. Several posts and videos here about the process.
If you are up for the oil cooler than the fan clutch is nothing? Check out this great write up...
::Water Pump Upgrade::BPD Water Pump Install Write-up::
You are looking at a couple of grand if you do the work yourself. If not, maybe look for advice here on a good diesel mechanic around you and get a second opinion and price for the work.
2005 6.0 Lariat Crew Cab 4x4 Short Bed
SCT X3 Tuner, Looney Tune from Quick Tricks
Bulletproof EGR Cooler (I live in CA, smog mecca)
FICM with Atlas40 from FICMrepair.com
Updated Standpipes, Dummy Plugs and STC
4" Turbo Back Magnaflow Exhaust
DC Power 185 amp alternator and wiring upgrade
CAT EC-1 Coolant
Dashboss Monitoring including pyro and fuel pressure