Photo Editing Assistance, Please!

I am having some trouble editing the following photo in Paint.net because my skills aren't all that developed. My goal is to get the flag out of the photo to make a skin with. The problem is that there's gaps in the flag where the door handle is and where the doors meet in the middle. I am trying to fill those spots in, but the picture has some glare and shading issues as it was taken outside, so when I try to fill the door crack, the colors don't match and it's very obvious what I did. The other issue is that when I paint over an area, that section is kind of flat whereas the rest of the photo has a shine to it because it was taken outside. Basically anything I add is really obnoxiously obvious. I only know the real basic commands in Paint.net so I don't know how to blend the colors or to easily select the areas I want to or even how to cover the gap where the door handle is.

I was wondering if anyone out there could take a crack at this or at least give me some hints as how to work on this. I am almost feel like the entire thing will need to be painted over to get a uniform color. If that's the case, how can I easily select the certain areas to work on?

Edited June 17, 201312 yr by neuronightmare