Help required... Apply within - Pi, Arduino and Automated Patio Doors

ok perhaps 10 seconds rfid trigger is a little unrealistic. i'll mount the reader in a specific place, at a specific height and the train the dog with beeps and stuff. that's easy.

linear actuator though, which sort? how would i go about working out the load the LA would be required to shift?

would a 'clunk click' gearbox work?

any help on which arduino hardware i should be looking at and how i'd interface it with the pi? (usb?)