I've done both items and you bet, both are DIY items.
One of my oil cooling lines leaked on my 1994 Ext Cab. GM sent me the wrong hoses and in fact, later told me my truck doesn't have an oil cooler. I had the build sheet to prove it. GM has tons of part numbers for the replacement hoses.. SO, I took them to a local Hydraulic Hose place and had them rebuilt. Cost $15 total! At the same time you have them off, replace that O-ring on the oil cooler mount. There is a Felpro set for that at your local auto parts store.
Tips I found: When removing the oil cooler lines, don't worry about trying to squeeze the quick-disconnect clips. They won't budge, just go ahead and unscrew the fitting from the oil cooler. (The radiator side is simple). BUT FIRST, mark on each cooler line a reference point so you know how to get them back on. If they are put on a little "turned" on the cooler end, they will leak. Hope this doesn't sound confusing, just mark.
Good luck! Pat