Don't use Linksys - folks here and elsewhere are less than positive about many of their items, especially their DSL kit...
D-Link make a well reviewed DSL Gateway/router for domestic/SoHo applications (DI-701).
The link below contains some comments from usrs:
http://www.macintouch.com/accessrouters.html#dlink
from: http://www.macintouch.com
(I don't work for D-Link; just appreciate a decent product...)
Useful sites:
http;//www.wown.com -(excellent tutorial site; includes assorted ICS issues and 'modem' sharing...)
http://www.timhiggins.com (useful links and deals with ICS/DSL as well)
http://www.dslreports.com (has very useful graphics displays on possible 'hook-ups' etc.). A good DSL info site.
Avoid buying a kit; you can do as well and maybe better buying the parts separately... Reltek make good inexpensive NIC's. Whichever you buy, ensure it's NE2000 compliant; most Linksys NIC#'s aren't... Netgear and D-Link cards usually are. If a card is NE2000 comliant it will happily advertise the fact. (NE2000 is an industry standard...)
Good luck