Door weather damage....

[phillymac23]

Well I opened the popup a few weeks ago and noticed that the caulk around the door had crumbled and the door is very week around door latch.  You will see in the picture that I did my best job trying to re-caulk the door and I think it should hold for awhile but isn't very pretty.  My question is can you get replacement doors?  Are the expensive?  Any suggestions on how to make the door stronger?  I noticed that the weather strip on the top also needs replaced.  Any suggestions would be greatly appreciated!

Thanks