you can still use the key as well as the button. wiring requires using the existing cig lighter hot wire on one terminal and tapping the other to the (you'll have to double check) fat yellow wire under the steering column.
be careful with the s2000 button, the terminals are very small - don't want to overload it and risk electrical issues.
also for the button, check this out - pretty close to the srt-10
[url]http://cgi.ebay.com/ebaymotors/Engine-Starter-Button-Push-Start-kit-FITS-ALL-CARS-_W0QQcmdZViewItemQQhashZitem588872e846QQitemZ38024 6353990QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccesso ries[url]
the problem with the other switches is they aren't flush mounted. you also want to make sure the switch has a good amperage rating. i used the factory switch so there was no need for a relay. wiring is very easy - on mine, it was a matter of routing the new wire so it doesn't interfere witht he tilt wheel and splicing it to the solid yellow wire under the dash.