If you use a solder sucker, make sure you use it better than I did... I went mains powered with a butane iron. Even though there's barely any room to get a solder sucker and iron over the holes, I managed to suck a big blob of solder, which fell right out and splattered over U603. The unit beeped and reset, then froze while booting.
I swept up the mess with the iron and figured I was boned... Finished with wick, which was WAY easier anyway. Forget the sucker for this job.
Turns out I got lucky... After a power cycle, this thing still works and looks as calibrated as before.
Incidentally, my controller board looks totally different from RadioFlash's... Mine has solder mask or conformal coating, and all the refdes are in the 600 range instead of 500. The manual on both Agilent's site and BAMA is dated 1986 and doesn't match at all. Most recent datecode that I saw here was 1987. Some web searching turned up a 1988 manual at
http://exodus.poly.edu/~kurt/manuals/manuals/HP%20Agilent/HP%203457A%20Service.pdf that seems to fit perfectly.
Mildly irritating that they redesigned it so thoroughly but didn't bump to 3457B. I guess since they didn't improve it, that didn't merit a change.
Well, all's well that ends well. Be more careful than I was. Also, once you've snipped the battery lead, make sure to hold it in the air. I had a close call where it sprung back down and tried to touch metal-cased C642.