Setting up audio / video conferencing projects

I’m excited to have found Asterisk and have a couple of projects in mind I would like to start. Using Asterisk or preferably Asterisk Now I would like some advice as to whether these projects would be feasible and how difficult they would be to setup for a tech savvy person using Asterisk for the first time.

The first project would be an audio conferencing system for a church for the aged or infirmed that cannot attend in person. We would tie the sound input and output from the PA system into the conference line with those that come in by phone.
Is this easy enough to setup?
Would each person dialing in need a DID allocated on the system or would a single DID work for everyone?
Is it possible for people to attend via PC (like a Netmeeting) rather than by phone?
Can I easily record the conference and distribute the recording electronically?

The second project would be an audio / video conferencing system for my company that would act like a ‘real time distance education system’. The video would NOT be cameras but rather the PC screens in an ‘application sharing’ mode. I want participants to be able to see what is on the screen of the ‘leader’ while they audio conference. I also want to record for later viewing the audio discussion and video from the PC screen sync’d together in something like an .mpg format for others to view later.
How difficult is this to setup?
Since this is a fairly generic requirement has someone already setup and configured this to make it easier to setup?