Dan,
I would be glad to help you with this project! It sounds to me like you are going to need a couple things in order to make this work. In addition to the low/high voltage wiring, you will need a common residential thermostat (you will only be using the Heating mode) as well as a 10-12kw heat sequencing relay to control the elements in stages.
Does your Oil furnace have a transformer with a secondary voltage of 24v? If so, you can use the items below for this project. If you do not have 24v you can tie into, let us know and we should be able to find something else.
Here is a link to a basic thermostat that should work for you:
http://www.northamericahvac.com/new-bra ... at-1-cool/ Here is a link for the 10kw-12kw heat sequencing relay you will need also:
http://www.northamericahvac.com/brand-n ... c-furnace/ Hope this gets you headed in the right direction. Let us know if you need further assistance!