You can find the Uboot instructions here
(also, because the instructions are a little unclear, the "reset" button is the power button. So, what you do is unplug the router, hold the power button, and plug in the router while holding the power button, and keep holding until it flashes 5 times (although for me, it only flashed 4, but it still worked fine). Then just follow the rest of the instructions.)
Just use the ITB file for the B1300 instead of the img file though.
I'm still having trouble getting it to work even after that though.
I go to http ://192.168.1.1, but it doesn't return anything. I think there's a probably with the file.