Since the only thing you are doing is to install a new module, and upgrade it to the processors release level, I would not even consider upgrading the systems unless there are issues with the current one. Correct me if I am wrong, but I am thinking you have the current release level manager software installed on site, just not at your office, and you were looking to pre-upgrade the module?
If that is the case, the upgrade will only take a power down long enough to plug the expansion cable in, and then once during the upgrade procees completion it will reboot. Hardly worth the time to pre-upgrade the module if you do not have the release on hand.
Upgading the system firmware almost always has some impact on the functionality, and it is rare when some configuration changes in either the IPO, or the VMPRO are not in any way needed. Some features change slightly in the way they work, and require some retraining, or fielding of calls saying it doesn't work the same anymore. I would not do that in a case where you are so far away unless you are planning on being there after you upgrade, and during regular business hours to cover these issues while onsite.
Also, since upgrading the release to a newer one will obviously take more time, and probably increase the customers cost versus just installing the module at the current release. You really should offer the new feature set to the customer, plan to utilize those new features with the customer to justify the additional cost they are incurring. Otherwise you are really wasting their money since it is not broken as is at the existing release.