Hi rkochis,
Yup, you now own'em. If you just want to manage the voicemail, then call in, identify yourself and have the employee transfer you to "777". You can now go into the admin mailbox and do whatever. It would be a very good idea to simply take control and change the passwords.
Create a proceedure that would only allow properly identified people to be transferred to the voicemail. I have not tried to dial in and just select "777" as the extension, it might work.
As far as Partner system programming goes, you need the Remote Admin. card. Or you have to talk someone through programming (yahoo). Just upgrade the software site by site to gain RAD ability. That's less than $200.00 per site CDN I think. What's that in USD, $20 ;-) .
-Chris