Here is an additional web site to check to get some information on the 138. It has good descriptions and some history on the enlarger as well as giving you some idea on how it all goes together. I think you will find the prices a bit high for some of the parts though.
Stonemills.et is a good source for parts for most of the Durst enlargers and processors. They also have copies of the 138 operating instructions and service manual. There is also a previous thread on this site from a month ago about the NEGA 138 and the LAPFE inserts for the various film formats. The LADANE 138 inserts into the NEGA 138 to allow you to print roll film from 35mm to 120. As you know by now this enlarger is built like a tank. It is an exceptionally stable piece of equipment. One piece of advice though is not to try and adjust the tensioning springs on either half of the enlarger without the proper instructions or tools.