I stripped 3 threads off of mine when removing/backing off the Hose Nut. I found that a Piece of broken off Nipple thread had corroded to the Nut. It acted as a cutter and damaged 3 threads on the way out.
As it happens oxidized Aluminum is actually hard and certainly harder than un-oxidized Aluminum; so, the stuck piece made a good thread cutter.
In the DIY section there is more specific Instructions. One of the Instructions was to use a Dremel type Tool with one of the tiny Cut off Wheels and cut a lengthwise slot on each side of the Hose Nut to the extent that you can get a Screwdriver in the slot, twist and split the Nut.
If you nick the Nipple threads that is not a problem because there is no sealing done by the threads.
DIY Repair Links
DIY Links by Parts Category - PeachParts Mercedes ShopForum
PeachPartsWiki: Do It Yourself Articles - Mercedes Vehicles
You may need to thin the Backup Wrench you use on the Oil Filter Housing Fittings that the Oil Cooler Hoses screw onto.
Added: At the Junk Yard I tried to remove the Hoses from an Oil Cooler and Stripped the Threads on one of the Nipples; and gave up on it.