The hard part for you, it would seem is the external access to exchange.
Presumably the IT guys will have a firewall around exchange and will
allow authorised users access from outside either by fixed IP or via a
VPN. If you know the addresses for the mail server and you have the
right access, then getting the email should be easy enough. I prefer to
use an XDA/iMate but any GPRS capable phone should suffice.
As to diary, much harder.
See http://www.ppcw.net/index.php for much more detailed assistance than
I can give here.

A Nokia 6100 for example will sync via Nokia PC Suite with Microsoft Outlook
97/98/2000/2002 for calendar, contacts and tasks.

I'd suggest the easiest way to get email would be to set up a rule on your
Outlook account to forward all mail to another email address that you can
access from the email facility in the phone.  There would likely be an issue
with large emails accessed by phone or by PDA (i.e. size) and with the sort
of attachments people send (e.g. Word, PDF are likely to be problematic to
display on anything less than a laptop).

Outlook server can be set up by the IT guys to provide web access but it
would obviously not fit on a small display e.g. phone and probably not on a
PDA either.