Well, sounds like you've got the VM answering when you dial 777, so the first step is done.
Assign each of the lines that you want answered by the Auto Attendant to CallDistGrp-7: #206-7-XX-1, where XX is the line number.
Set the HuntDelay to "Delayed", which is 4 rings (your only other choice is "Immediate", which is 2 rings): #506-2
Set the Auto Attendant to answer either Always, Day Only, or Night Only: #507-X, where X=1 for Always, 2 for Day Only, or 3 for Night Only.
Set the Transfer Return Extension for EACH voice mail port to Ext. 10: #306-XX-10, where XX is the Voice Mail port's Extension Number.
Do you REALLY want Ext. 10's mailbox to answer EVERY call transferred from the Auto Attendant and unanswered? Or do you want individual mailboxes to cover unanswered transfers, and Ext. 10 receive the "dial 0 and timeout" calls?
For the first senario (Ext. 10 takes ALL messages), assign Auto VMS Cover ONLY to Ext. 10: #310-10-1. Do NOT assign it to any other extension. Calls will transfer from the Auto Attendant to the selected extension, and if unanswered, return to Ext. 10, and if still unanswered (or if Ext. 10 is in DND) cover to mailbox 10.
For the "normal" senario, assign Auto VMS Cover to every extension that has a mailbox. Calls transfer from the Auto Attendant to the selected extension, and cover to the extension's mailbox if unanswered. Calls to an extension without a mailbox (like a conference room or break room), cover as above.
Good luck!!