We finally are rid of our bad A-Frame. Many thanks to everyone who posted suggestions here.
On recommendation of Roger Baughman here on the boards, we went to E & C Spring Inc. at 518 Venture Street in Escondido CA 92029 (760-747-5050 or 760-747-1961). Owner Ben Elkins was extremely knowledgeable, helpful, and professional.
For the record, we asked about straightening the piece, and his opinion was that it should come out to be straightened anyway. And his further opinion was that the tube was badly enough damaged that he would actually cut that section out and replace it. Since we had a good take-out, all that was moot.
The infamous hinge pin that is reputed to be the source of all trouble with this job turned out to be no problem. The pin came out with a combination of an air chisel (with a flat drift head on it) on one side, then a short section of pipe and the original nut as an extractor from the other. And the pin went back in with some coaxing from the same air chisel -- no need for the dry ice routine.
It turned out the thorniest problem was removing the bolts holding the other end of the arm to the frame. At least one nut was frozen on, and the A-frames on both sides are through-bolted, so bolts needed to be moved around to keep the other side in place during the procedure.
My bill was for eight hours of labor (split between two men), as I had supplied all the parts. In addition to the take-out A-frame, fellow BBS member Russ Barnes had also furnished me with four new bushings and pinch bolts.
Now that the A-frame is done, we are on our way to L.A. Freightliner to have the bearings looked at and the alignment done. We normally stay out of these sorts of major shop operations, preferring smaller shops where the service is somewhat more personal. But getting parts or even drawings and service instructions for our weird Mercedes axles is something of a challenge, and Freightliner is Mercedes' official US service channel. We chose the Los Angeles location because BBS member Tom Christman happens to work there.
Once the bearings and alignment are taken care of, we'll proceed directly to a tire dealer for six new tires, as we're now well below legal tread on all four drivers, and the steers are so lumpy they are rattling our teeth out.
I'll be writing this up on the blog shortly, and we've got loads of photos of the process, so we'll pick a few to post there as well.