OT-Packet sniffing, ssh and private ips

[Steve <sgulick poboxes com>]

Please forgive me for I am new to all this and have been curious about this
topic for some time.

I am running rh6.1 on 3 boxes on a private network behind a single box running
ipchains/portsentry on a public ip (cable modem) The firewall box has 2 nic's
one for my public ip address and one for my private network ip address
(192.168.X.X).

I am the sole user of any box on the private network.

My question is if I am going to telneting from a box on my
private network network to the private nic on my firewall do I need
ssh? And can some one sniff these packets from outside my private network?

TIA

Steve