Take out the old one first. Verify dimensions and mounting arrangements. As Neal mentions, there is an international standard but there is also variety between manufactures (patterns may be same, but bolt sizes different).
We had to change our tele-vator TV on our Canyon Star. We just picked up a Walmart special since we knew we were trading coach in soon. Mounting in tight configuration, with non mechanically inclined DW as helper, activated my colorful naval language skills. Also left me with some new scars.