Picked up the S138 the other day. Since I've always found a lot of useful information in old threads, here are my thoughts on my original questions for posterity sake now that I've dismantled the enlarger and gotten more info on it.
1. When dismantling the enlarger, the key to the warning in the original quote above is to ensure that the enlarger head is at its highest position before you release the lever that connects the top half of the column to the bottom half of the column. If the head is not at the highest position and you separate the two halves of the column, then you risk inadvertently pushing the lever that is used to move the head up and down while on the column. If you do this, the spring will shoot the top half of the column away from the enlarger head until it reaches its end position (as opposed to slowly lifting the head up to the top as it would if the entire column was assembled). Even though the column would only move a few feet it would definitely injure you if you were in its way. Hopefully this will help someone in the future.
2. Based on my discussions with a few people, I'm pretty convinced that the Durst 1200 is a better choice than the 138S for someone working in 4x5, 120 and 35mm. It seems that for 35mm, the 138S is a bear to work with.
3. Many thanks to Philippe. I don't have the right type mount to do what he suggested right off, but I'm pretty sure I can fashion one.
All the best,