I have had three of these. The enlarger can be broken down fairly easily. To answer your question, the head will remove from the carriage by loosening four retainers (this will require tools). Some of these are allen head and some are Phillips head. Lower the table and the head as much as possible befor you begin doing this.
The column can be separated at the center by loosening two retainers (all that I have seen are knob type retainers) The table is removed from the support by loosening the center knob. The column is removed from the base by loosening knob type retainers.
Ultimately the enlarger is broken down into five major pieces.
I would recommend removing the front surface mirror (open the head front access panel). Also remove and securely package the condensors, the UV/heat resistant glass, and the light bulb.
The Durst 138,138S, and the 139 do share a large number of parts but there are distinct differences between these models.
Durst does recommend, for best performance, the appropriate condensors matched with the proper focal length lens to accurately collimate and focus the light bundle at the nodal point of the lens. For 5X7 these would be a pair of 240 condensors matched to a 210 mm enlarging lens. For 4X5 these would be a 240 condensor in combination with a 200 condensor matched with a 150 mm enlarging lens. As focal length of lens is changed the condensors should be changed to those that are appropriate. These condensors include the 85, 130, 160, 200, and 240. There are also specific condensors for differing light sources. For instance a point light source requires specific condensors that are different from the more common.
There has not been any one single change that I have made in the last twenty one years of photography that has materially improved my prints as much as switching to the Durst condensor enlarger. Good luck with your purchase.