configuring firewall for remote assistance

There are some MS instructions regarding firewall configuration
for the purpose of running win xp remote assistance.
MS states only the port 3389 shall be opened.
But more details on that filter rule are missing.

1. Does it apply to the novice's or the expert's PC ?
2. Is that for inbound or the outbound traffic ?
3. What protocol is this for, TCP or UDP ?
4. What application has to be associated with this packet filter rule ?

I'g going to run win xp remote assistance in following configuration:
- expert's PC: win xp pro sp2
- novice's PC: win xp pro sp2
- both PC's connected to internet via DSL modem and win dial-up connection
- on both PC's kerio personal firewall running, no router hardware
- both PC's operate in single, no LANs present

How exact should the firewall filter rules to be set for both PC's
if the novice's generates invitation from Win Help and Support application and sends it to expert in a file ?

How exact should the firewall filter rules to be set for both PC's
if the novice's generates invitation from Win Help and Support application and then his choice is the win messenger to send the invitation ?

How exact should the firewall filter rules to be set for both PC's
if the novice's does not use Windows Help and Support application at
all but starts the windows messenger to invite expert to assistance ?

 

have empirical found out the appropriate filters.
Somebody interested too ? let me know please.