You cannot switch presets in Gearbox with any pedal.
You need to upgrade to POD Farm 2 and use the Set List feature to change presets. You can use something like our FBV Express or Shortboard MkII pedals.
Here's a tutorial that shows you how to do that:
Yes, you can set a pedal to toggle an amp model on and off to toggle between the two via MIDI. IN POD Farm 2 there may be a small amount of latency, but you should give it a try to see if it works for you.
First, connect your Line 6 gear to Line 6 Monkey, and in the Optional Add-ons tab, click on Activate Purchase, and in the window asking for a license key, type in the word:
all in lower case letters. Then, check to see if there is a check mark next to POD Farm 2 in that window. If there is, you can download the POD Farm 2 software to use with the interface from the downloads page:
If there is NO check mark next to POD Farm 2 in that window, you will need to purchase the license: