So, about those instructions. An important thing to know is that the model number of this router is F7D7302, which is just a newer version of the F7D3302. So when you're searching for firmware that's the model you want to use. Now, I've spent some time doing research to get this working with TomatoUSB and finally came with a pretty simple solution. I've noticed a lot of guides want you to install DD-WRT first, which is completely unnecessary.
The best version for this unit right now is the TomatoUSB builds from Toastman. While this may appear to be a lot of steps, it's really not all that complicated.
You're going to want two files for this procedure. Google "tomato toastman 4shared" to find the repository (it's hosted on a download site called 4shared). You'll be looking for the latest version in the RT (MIPSR2) folder (each version will be split into VLAN and STD versions, you'll want the STD one). Inside of that folder will be a bunch of .bin and .trx files. You'll want the .bin file tagged "tomato-F7D3302" and one of the .trx files that starts with "tomato-K26USB-1.28" (you do not want the NVRAM versions of this file). I'd recommend getting the -Ext version of it as it includes all the features.
At the time of this writing I'm using the following versions: tomato-F7D3302-1.28.7501.2MIPSR2Toastman-RT-Mini.bin tomato-K26USB-1.28.7501.2MIPSR2Toastman-RT-Ext.trx
Connect the router to your Mac/PC via Ethernet, you should be assigned an IP in the 192.168.2.X range.
Perform a 30/30/30 reset procedure to enter CFE mode. (Hold down reset for 30 seconds, while still holding the reset button unplug power from the router and wait another 30 seconds and finally plug power back in while still holding the reset button for an additional 30 seconds.)
Navigate to 192.168.2.1 in your browser and navigate to the .bin file you downloaded earlier, then click upload. If nothing happens after a few minutes, try hitting the upload button again or reloading the page. It took two tries before it took for me, but once it did it was basically instantaneous. A new screen will flash by letting you know the firmware is being installed and the router will reboot.
When it comes back up it should still have the same IP as before, but this time it will ask for your a username/password. It defaults to admin/admin. Go ahead and login, congratulations! Tomato is now installed, but we're not quite done yet...
In the new Tomato interface, go ahead and navigate to the Upgrade section and point this at the .trx file you downloaded. Tick the box to erase NVRAM (which will delete all your settings) so that you can start from fresh and don't have to worry about issues cropping up later.
That will take about 5 minutes to complete, when the unit reboots it will now have a default IP of 192.168.1.1. You'll need to set your machine to have a static IP in that subnet in order to access it. Once you do, you're all set!