Meta Fields in my plugin

Hi All

Ive been making my own plugin. In short its for making bookings for hotel rooms. However, I have some fields in my booking form that I need to automatically populate when a specific hotel room is chosen from a drop down list.

Field A: Hotel Room Name (query = all posts from hotel_rooms post type in a select box)

Field B: Check in Time. The check in time is unique to each hotel room and when the hotel room is selected on the booking form I need it to query the selected post (from hotel_rooms) and show the check in time meta information.

Ive read in a few places this can be done with ajax, am I right?

Im guessing the process would be something like

selectbox > onchange = fire a ajax call to query the selected post ( from hotel_rooms post type) for the required meta information (Check in time).

Thanks