Update - I upgraded the 128 GB ssd to a 256 GB ssd. I purchased this sdd on Amazon:
Lite On Plextor M5M 0.85-Inch 256GB mSATA Solid State Drive (M5M 256GB)
Whatever ssd you buy, it needs to be an mSata ssd - they are very tiny. (Neither a 2.5" ssd nor a 1.8" ssd could ever work - they are way to large and would not fit the adapter any way.)
I also purchased this case for an mSata ssd:
MyDigitalSSD Bullet Proof USB 3.0 mSATA SSD Enclosure Adapter - MDMS-BP-USB3
You should guard against a static discharge before opening the case and while working inside the Vizio. Don't touch anything unless you have too!
Before I replaced the ssd, I placed the 256 GB ssd in the mSata enclosure and used dd to clone the 128 GB. It took dd about 10 or 15 minutes as most to clone the 128 GB drive. I also made backups to dual layer DVDs and blu-ray disks.
Make sure first to detach the AC adapter if it's attached to the Vizio!
I gathered my courage and took off the back of the Vizio 14" thin and light laptop. You need a special screw driver tip (star-shaped - not sure what the proper name is) to remove all of the screws on the back cover.
I lifted the back starting at the hinge (because there are some flanges at the other end.
With the large flat battery at the bottom, the tiny mSata ssd is in the upper left corner held in by two screws.
Caution: You should (must) remove the battery first to avoid damage! On some laptops you can just unattach a connector to the battery. In the Vizio, you must remove the five screws holding the battery to the case in order to detach the battery (not such a great design but easy enough).
Once the battery is removed, you can easily remove the 2 screws holding the ssd in place. The ssd will pivot upward when the screws are removed making it easier to pull the ssd out of the connector.
Insert the new ssd, pivot it down, and re-insert the 2 screws.
Reattach the battery and re-insert the 5 screws.
Attach the back cover - make sure you get the little flanges (at the bottom where the battery is) in first, and close to the hinge side. Make sure the cover is correctly positioned and then re-insert the screws.
If your Vizio is the same as mine, after re-assembly, if you press the power button NOTHING will happen. Don't panic! (Although I almost did.) I had learned previously from removing the cover you must plug in the AC adapter, and then press the power button. I'm not sure if this is due to just removing the cover or removing the battery (but I think it's just from removing the cover).
After the intial boot, you won't have to have the AC adapter plugged in - it will operate as usual.
My Vizio has 4 primary partions (one extended) so even with the new ssd, it took a bit of work to make the new space available. There is a primary partion of about 2 GB at the upper end of the first 128 GBs that may be used for Intel's Rapid Start Technology. This was enabled in the bios - but the Vizio seems to start up/hibernate just as fast with this disabled. The partition has id 84, btw. In order to make the new space available, I had to delete this partion using a Ubuntu Live CD (which I booted the Vizio). I also made sure I turned off swap so that the Live CD would not try to use the swap partition. (My Vizio is set up to dual boot the orignal Windows 7 that was pre-installed and Ubuntu 13.04.) Once the id 84 partition of 2 GB was deleted, I could then increase the extended partition size, and add one or more new partions within the extended partition. (You could also add a new primary partition - but then you can't re-install the id 84 partition.)
If you are careful, you should have no problems. The Vizio is easy to disassemble and re-assemble. I have no idea why Vizio insists that users can't upgrade their Vizio's themselves. Replacing the battery is very simple also. There is no need to send the laptop back to Vizio.