I'm going to try the instructions for the original Transformer:
http://androidadvices.com/how-to-update-asus-eee-pad-transformer-tf-101-to-honeycomb-3-1/
Procedure to update Asus Eee Pad Transformer:
First up you will have to download the Zip file of Transformer 3.1 Update in which you will find the update file which you will have to download in your computer.
Now, up next with the help of the USB cable just connect the Asus Eee Pad transformer tablet with the computer in which you have extracted the file so as to copy the extracted file in the tablet.
Now, after extracting the file, just simply copy this extracted file in the Transformer tablet in the SD card and please note that don’t place the file in the inside of any folders, if placed so the file won’t be detected as an update file.
Now, after this simply turn off the device and after that press the volume down key and then the power key till the device boots up in the ROM Mode after which you will have to press the Volume up key after which the updation process will be initiated after selecting the file which you have placed in the tablet.
After the process is started, the device will take 5 – 10 minutes of time while it applies the update. As soon as the device is updated the tablet will be rebooting automatically and then a user notification will be popping up on your dock station stating the update availability notification to the version of 0209. Just follow the on screen instructions to proceed for the update and then there you go, you are ready with the update on your device