public key access from a Lan to a public server

hey friends,

 We are going to setup one Public Server/Live Server with FC3.I wanted
to use public key as authentication for allowed users for SSH login.

We have one public ip address for our Lan and our Lan is behind the
Firewall .I have few questions:

My Network Scenario:

Public Server Named:  Machine A with public ip address.

My Lan Gateway Named: Machine B with public ip address.

My Lan with 25 Machines with private ip addresses {192.168.1.0}
Machines from C to Z

a) Is it possible to access the Public  Server wtih public key
authentication if the Lan is behind the Firewall and the machine is
having the private ipadresses with the gateway of the Lan having
Public Ipaddress.


b) Now I want to access through my Lan(Machines from C to Z) the
Machine A using Public Key authentication.Is it possible to access
Machine A from any Machine in My Lan through Public Key Authentication
,If yes then how to do it and what are the problems/risks in doing
that.

c) I want to access Machine A from any machine .Means through any
machine I should be able to access Machine A through Public Key
Authentication,If yes then how to and what are the problems/risks in
doing that.

Currently I am using FC3 with 

openssh-3.9p1-8.0.2
openssh-server-3.9p1-8.0.2
openssh-askpass-3.9p1-8.0.2
openssh-askpass-gnome-3.9p1-8.0.2
openssh-clients-3.9p1-8.0.2

Please let me if you need any other inputs.

Thanks & Regards

Ankush Grover