cgashlin01,
There isn't a guide for specifically setting up the 5000 with an Asterisks on the Mitel site. Normally we work with the Asterisks Technician/Engineer to determine what each system is capable of doing and then configure it from there.
If you can tell me how you setup your Asterisk I can help you set up the 5000 side. To be honest though the 5000 doesn't require a lot of programming to get the trunks up and working and most of it would be in the Call Configuration of the SIP Peer Trunk Group. The biggest thing, really the only thing, is to set the DTMF Encoding to RFC2833 and Speech Encoding to G.729.
Thanks,
TE