Migrating from jQuery/jQuery UI & hosting architecture

Migrating from jQuery/jQuery UI & hosting architecture

Hi,
I have seen a couple of posts here that touch on the subject, but I'm still a little unclear.  If I'm migrating an existing site that is based on jQuery & jQuery UI & other widgets (and that currently has no special forks for mobile device rendering) what are the recommended ways to address the following:
1. Should I set up a "mobile" subdomain within my hosting architecture (e.g., mobile.mysite.com)?
2. How should I best distinguish mobile & desktop user agents and where would I best make that determination?
3. Should I limit my use of jQuery & jQuery UI to the "desktop user agents" and jQM to the "mobile agents" respectively?

Hope those questions make sense!  Any suggestions would be really appreciated.
-Mark