Assuming the calendar in question is already a recognized graphic file (TIFF, PSD, JPEG, etc.), then you would use the Place feature to add the file to the document you're working on.
The Place feature is found in the main File menu; File>Place...., then select the graphic you wish to add.
The other way to do it is if the calendar file is open in another document file in Photoshop, by duplicating the layer into the document you wish to put it in.
No Photoshop CS5 and Photoshop Elements are separate programs.
CS5
yes.
Photoshop CS5
Photoshop CS5
Yes, you can upgrade from Photoshop CS3 (or earlier) to Photoshop CS5 Extended, no problem.
cs5 is better
Adobe Photoshop CS5
In Extended version you have 3D Tools to work with 3D Objects.
Adobe photoshop CS5 (extended)
Adobe Photoshop CS5
Go to C:\Program Files\Adobe\Adobe Photoshop CS5\Scripting in Windows XP or find Photoshop\Scripting folder on your computer for detailed information's.