Exchange Server 5.5 removal and replace by 2003

Right then where to begin.

We have a current setup operating on two windows 2000 servers with a trust relationship to an NT4 domain, in addition to this we also have an exchange 5.5 server running in it’s own domain.

I am trying to upgrade the mail services from 5.5 to 2003 but in order to do this I need to be able to see the exchange 5.5 objects in the AD which at the moment I can’t as it’s connected through a trust. Is there any issue with moving the exchange 5.5 server from it’s current domain and importing it into the mixed mode 2000 domain? i.e. will I lose connectivity to exchange etc. also will this then allow me to migrate users from 5.5 to 2003?

Thanks in advance for your help.