Hi, I've done the Upgrade to 2.3.5 without any problems.
Did you Download the File from Huawei to your comp?
If you open/extract the File - you will find the Set up instructions which you can print out.
I have a Micro SD card holder which plugs into the USB connector on the comp. It's a Transcend P3-022311 S/N:P00460 which I purchased with a 8GB card.
I can then load Apps or Upgrades directly onto the card, then insert card in the phone and follow the set up instructions.
The Volume control button has Vol+ & Vol- (it's a rocker switch) so all you have to do is use your thumb and index finger to push the button while you push the Power button on the top with your index finger on your other hand.
*The trick is to do this simultaneously. If it doesn't work - pull the battery out for a couple of seconds - re-install battery and try again*
I find it easier to leave the battery cover off while doing this little exercise.
Make sure that your battery is as near full charge as possible before you start and wait until it completes the upgrade (as per the instructions).
Let's know how you get on. Neil.