These are instructions for upgrading your older Toastman build on Linksys E3000 router to the latest firmware version. If you have never installed a TomatoUSB on this model router, you may want to start here first.
Download latest version of the either "STD' build or VLAN build (if you are using VLAN feature) from here.
This is the version I have upgraded mine to:
Log into your router's web UI by entering the router IP address in your browser window.
Select "Administration-->Upgrade" option from the left nav bar.
Click on "Choose File" and select the above downloaded file. Press Upgrade.
I did not select "After flashing, erase all data in NVRAM memory" option, as I wanted to give it a try first without erasing all my old configuration"
Depending on how you are connected to router, it should take less than 4-5 minutes to upload the latest firmware image file to router and then another minute to restart your server.
Through these steps, I have successfully upgraded my old 1.28.7490.2 build to latest 1.28.7503.7 build without erasing NVRAM memory.