install/swap procedure

currently have 3.7 on a 6.03 box that would like to swap out for a new
box running 3.8/6.5...

the new 3.8/6.5 box will assume the exact same roles as the 3.7/6.03
it is replacing, which is just about everything - DNS/DHCP, firewall,
proxy, cache, lots of natting, etc.

it would be swell if i could configure the 3.8 as identical as
possible and as far as possible before pulling the plug on the 3.7...

so far have just begun installing 6,5 and am mulling over ip config...

can't find a recommended strategy for this particular scheme in cj's
book or on the kb. would appreciate any tips...

cheers...