Using a slow hub between the two systems negates any possible issues with autonegotiation, yes. It may not be necessary in your case but it helps eliminate a variable.

Also, assuming my rusty memory is correct remember you'll have to use Open Transport rather than "classic" MacTCP to use DHCP. (Which is what OS X's Internet sharing uses. The "Dynamic" setting you see on the MacTCP control panel is a proprietary AppleTalk-related thing.) This probably won't be an issue, depending on what System version you're running on the Quadra. Worse case you can always set a static address anyway.