Hi Jeff,
I got the driver's side done this weekend. As I suspected, the most difficult part was completely removing the battery tray. You have to remove the induction hose to be able to really get to the ECU connectors (be VERY careful with them!). The only other thing that was slightly challenging was removing the plate covering the mount out from under the airbox. If you don't have another person to help, you will likely have to remove the airbox to remove the plate.
The driver's side mount was not in good shape. It wasn't making a ton of noise but there was a TON of movement in it. If you are doing the inserts, make sure to buy a brand-new OEM mount as it's likely your existing mount is in bad shape. Ford definitely cut cost by not designing a more robust mount for the ST. I would say a new OEM mount is almost a requirement at this point. They are so cheap to buy.
Make sure to use some sort of Lithium grease of CV-Joint grease when installing the insert. It will go in much more easily and will prevent squeaking later on down the road.
I am incredibly happy with the results. The passenger-side only made a big difference, but I could tell that there was a lot of movement on the driver's side. Now, there is next to no movement, even on hard shifts. The increase in vibration is minimal. As I mentioned before, the yellow street version should be more than enough for daily drivers.
A little side note: When you reconnect the battery, your auto-up driver window function will no longer work. You will have to reprogram it. It's very easy. The link is here:
http://www.fiestast.org/forum/fiesta-st-electronics/1307-window-auto-up-not-working.html
I thought something had shorted until I used my trusty friend, Google. Thanks for your offer to help out!
Ron@Whoosh, thanks for sending these out so quickly!