Confused about Exchange 2003 and Terminal Server licensing


Part A - Confused about Exchange 2003 licensing

I have a Win 2003 server running Exchange 2003 and I have 15 users. 
This was setup by my predecessor, and now I am responsible for it.  I
can’t find out what he bought in the way of licensing, and he is not
reachable to call.  My boss wants me to add 35 users ASAP.

1 – Where do I go to purchase the licenses?
2 - How much will they cost each, roughly?
3 – How long will they take to arrive?
4 - What would happen if I added them right away, before the licenses
arrived in the mail?  Is there a grace period of 120 days when those
accts will be allowed?
5 – We are in the MS developers program, and get some amount of
licenses as part of this.  Any idea how many or how this fits into the
picture.

I think this server was originally an exchange 2000 server with the
same 15 users, but I am not sure.

I found many links to web pages about MS licensing, but I am still
confused.  Any help would be very much appreciated.


Part B - What are my options for Terminal Services licenses on Win
server 2003
I also have an Win server 2003 that I am running Terminal Services on.
 It came with a free (and built-in) 120 day license. Now that has
expired.

What are my options about getting it to work again?
If Win XP Pro machines connect, do I need licenses for them (CAL
tokens)?  Someone told me they already come with one since XP Pro has
a limited TS built-in.

Thanks in advance,