New ATV owner of a 250Ex and 400Ex

Hello I just purchased 2-2007 250EX and 400 EX. The previous owner said they sat in the garage for a year. I tried starting them up and they dont stay on very long after I release the throttle. Never owned any before so I am new to this. What things should I do before my first ride which will be in the sand dunes? I'm assuming oil change, filter replaced(on the 400 only which I just found out) what else? Thanks in advance for the help.