Keezer help

Just bought a 5.5cf chest freezer from craigslist and I am excited about the keezer project. Freezer cools just fine. My plea for help is with the thermostat. I am totally illiterate in regards to the internal thermostat and need some help. I know that an external one will do but I am looking to do it a little cheaper internally and would love to learn about the process.
Ebay has so many options and I’m not sure which will work etc so I was hoping that a few of you could send some links here as to which ones would do the job. I think the switch needs to open when it gets to cold and close when it gets too warm. I just want the right one the first time without having to learn the hard way. Thanks for your time!!

Ebay links or links to other sites greatly appreciated

That is pretty much correct. I much like youself purchased a keezer from craiglist. Mine however had already been converted to a kegerator. Best $25 I ever spent, considering it came with a CO2 tank, all the lines, and a single tower. However, the guy I got it from did not homebrew. He had purchased it from someone else who had put in a thermostat like you are wanting. He said when he went to adjust it, because it was starting to freeze, the thermostat poped and smoked. So he quite using it. The connections were not done correctly. He did the right thing because it was a firehazard. However upon rewiring the freezer, i figured he blew the thermostat. It was around $50 for a new thermostat like you are wanting. On top of that the wiring to put it in place, and the experts at the appliance parts place were not certain on what one it would need to get the freezer to run say 40-55. Save yourself the time and trouble and just spend the extra $15-$20, its well worth the time and hassle.

Hey that's great input and i appreciate the advice but I know there is a method to the madness out there. Any more input out there? There are hundreds of thermostats on ebay. One of them must work.
Thanks again for the post. Seems like you have a great unit.