Exchange 2010 Coexistence

Exchange 2010 Coexistence Question:

I am in the initial planning phase of installing a new Exchange 2010 server in our organization. I have done quite a bit of research but there are still a few things that are not clear to me. We are currently running an Exchange 2003 server. My plan is to install 2010 in coexistence with that server. Here are some of the questions that I have:

1. Is there any reason that I should not prepare the AD schema now? I may not install Exchange 2010 for a month, but I was wondering if will hurt anything if I run the schema updates ahead of time.

2. The first role that needs to be installed is the Client Access role. We use ActiveSync for our mobile phones. Is there anything that needs to be addressed prior to installing the CA role in regards to ActiveSync? I know firewall rules, etc. will need to changed eventually to accommodate the new server, but is it necessary to do it prior to installing the CA role on the new server?

3. Are there any other pitfalls that some of you may have come across with a similar installation scenario?

Thanks