gas cap door

I have a 1998 plymouth neon. I need to replace the gas cap door,its broken off... how is it done? thanks...

Have you looked at it? Just a couple of allen bolts I believe.

Thanks, yes I did look at it. It is broken off at the plastic hinge. the gas cap door was hit and snapped off. I opened the trunk and cant get to it from there so I felt under the the passenger rear wheel ( at the top) and felt an area where there may be and access point .I will look at it further in detail this weekend. ( its the sons car and he is NEVER home).
thanks, will keep you posted.