Gateway / Port redirection

[Tech Support]

Background

I am currently running freeBSD 4.8 on a box as
a) a gateway for the house for internet access on dialup permanant IP
, domain etc
b) using apache for a web server hosting a domain and virtual domains
c ) Qmail for mail
d ) Squid proxy for the childrens computers access ( saves on
bandwidth )
e) ProFtp as FTP Server
f ) DNS
g ) Ssh
h) All on a dial up account
i )  port Sentry
j ) etc

I need to run a couple of programs inside the lan where ports are
directed to them from outside  the lan  eg all the above services are
located on the Bsd box ( 192.168.x.x ) and i need to direct port 5060
to 192.168.0.7 ( for arguments sake )

Not being very knowlegable about the inner workings of FreeBSD ( but
learning slowly ) I have decided that seeing as this is really only a
temporary exercise ( perhaps a month , and to compound everything in a
couple of months the BSD box will also be shifting to broadband ),
that I would use FreeSCO ( www.freesco.org) as a NEW gateway / port
redirector .  I am going to forward my current services above to my
current BSD box and the NEW PORTS direct to the Win box(s) that I need
to test this software on . My thoughts were to leave the current
gateway as 192.160.0.1  and the FreeSCO box name it 192.168.0.254 . I
would like to direct outbound web surfing via the BSD box as current
as it would be a PITA to change all the machines on the LAN

My question(s)

a) is this overkill ( is there an EASIER way to do what I want ( port
redirecting ) ( bearing in mind that although the lights are on in the
attic they are at times low wattage :-)  )

b ) WHAT do I need to change on my BSD box ( rc.conf  etc ) to make it
work the way described ? Remembering that this is only temporary .

Thanks in advance for any advice

Regards

Benny