Therer is a really good DIY for doing all of that using an audrino
AutoTop DIY
you would still need to do a handbrake and moving hack.
there are a few threads on that as well
The problem I see using the relay you found, which is cool!, is will it stop motion if you press the button again
You need to be able to manually move the top as well as stop it in an emergency
The arduino project does just that