HELP : asterisk as call agent using mgcp?

hi its interesting to be in this forum a lot of information about asterisk here…
pls help me in the following topics
1)how to configure asterisk as call agent or media gateway controller
using mgcp
2)how much mgcp will asterisk support (max: capacity)
3)can sip be used as user agent with mgcp being a call agent

Please do not double post.