my friends and i shot a pretty funny short last night about 3 drunks who spend a night together in one small apartment (in which only one of them actually happens to live) and never see eachother once throughout the whole escapade..
we used an entrance on the side of my house and put a number on the door to make it look real. then i thought it would be a good idea to put two different numbers on the door and shoot from an angle to show that our apartment (21 B) is located in between two very similar looking ones (21 A and 21 C). since the door was near the corner of the house, i took each of the shots from the same angle, figuring i would just flip one of the images in post...

naturally, the number is also flipped so my 21 A looks like: A 1 backwards 2... not good.

i do not have photo shop, and i am not too skilled with the FCE yet so my question is if there is a way for me to cut the correct 21 A from the original shot and paste it over the backwards number in the flipped shot..

Yes, but the angle may not match, causing it to look dreadful...

Put your correctly oriented shot of the number 21A layered above the flipped shot on track V2.

Go to the motion tab for that clip in the viewer. Adjust the cropping, and raise the number for feathering. If that doesn't look good you'll need to use an 8 or 4 point garbage matte (video filters menu) instead of cropping.

If nothing works send me a full quality frame export (File>Export>QuickTime>Format=Still Image) and I'll send you back a Photoshopped PNG file that you can drop over your clip