Mike...first: take your time.
Second: you should gather all relevant documentation (like gathering optiPoint 4x0 HFA Manuals, related released software Release Notes, the Siemens Expert Wiki I pointed you yet) before doing something that could become potentially problematic (irresponsibe phones, Boot issues and so on...).
Third: read them carefully (you'll able to find there all you're looking for, tips and tricks too).
Finally you will be able to perform the software upgrade by hand (without DLS) phone by phone without issues.
Regards,
Kimera.