The easiest way to access files remotely is to use Back to My Mac:
OS X Mountain Lion: Use Back to My Mac
All you need is an iCloud account which is of course free. iCloud needs Lion, and so will your iMac.
There are a number of elements involved that must be working, and will not be possible for you to configure while you are away. Read the following and use it as a checklist to ensure all those elements appear to be correct before you leave again:
Setting up and using Back to My Mac with an AirPort base station or Time Capsule
OS X: Using and troubleshooting Back to My Mac with your iCloud account
Once everything is configured properly, it just works. You can log in to and use your iMac at home, including using its iPhoto, and copying files between it and your MacBook Pro, while you're on the other side of the world:
OS X Mountain Lion: Share your screen using Back to My Mac
If you have time, take your MacBook to a coffee shop or someplace with a public Wi-Fi network, and verify it works before you go away again. If it does, it should work anywhere in the world.