must be a simple solution?

Please help this lost little puppy.

Initially with this:
Broadband service (Telewest) coming into cable modem. I would like to connect this badboy to my Mac G4 (OSX 10.3.9) via ethernet. sounds awefully simple. but can anybody walk me through the settings? (DHCP etc.) i seem to be having no joy. pop-up keeps telling me connection cannot be found (or words to that effect). rather annoying now.

Then in time:
Would like to (again) connect Mac hard-wired into modem and/or router, as plans are to have a PC wirelessly connected in a diff part of the house. best way? ditch the modem altogether and get an ADSL router? suggestions please. and setting walk-throughs if poss.

and be clear as poss. ain't stoopid but i need to be sure. many thanks.

For the first part.
Under TCP/IP set it to automatic and be sure that you have registered you MAC address with Telewest as thats what i had to do with my uncles machine and he is with telewest. The MAC address is your ethernet ID

The in time part go buy a wireless router with an inbuilt switch then that will be all you need. Dont buy any ADSL stuff as you have Cable they are two different things