Richard,
I dropped the contents of the IC2 API archive ( ic2/ ) into the MCP decompiled code location below and Eclipse picked it up like a champ:
$MCPROOT/src/minecraft/net/minecraft/src
( $MCPROOT is just wherever someone installs the MCP core components )
Thanks for the guidance on this! Time for me to break stuff (and learn in the process).
--Elector