- Do I need to break/crush these down at all or is it okay to let them decompose on their own?
It is perfectly okay to let them decompose on their own. Breaking the fruit down will accelerate the process, but it will happen no matter what.
- The area I am putting them at used to have rubble and random landscaping ruins that I've mainly cleared out. Can I start compost over this?
Yes, you can compost there. Having 'good soil' underneath the pile can help worms and other critters find their way into your pile, but it will compost either way.
- Also this is about 50 yards from our neighbors back side of their house and 5 feet from their lot... is this ethically wrong??
I don't feel that it is unethical. If the neighbor uses the part of their lot right against yours in a way that your compost might be a nuisance, talking to them first might be neighborly but not really an ethical concern in my mind. 50 yards from their home is plenty far.
- Do I need to add anything specifically to get this started? I will be grabbing some compost from the local brush dump to help.
Not really. Fresh compost might seed some organisms to get it started sooner, but there really isn't much you can do to stop composting. The relevant players are in the world all around us and will find the compost pile in time.
- How often should I mix the pile during each of the seasons? We are in Minnesota.
This is entirely up to you. In the frozen months your pile will probably have a frozen crust at the least that will make turning impractical. If the compost is active at all in these months it will be because of the still-warm inside, so turning would slow the process.
In warm months, you can turn the pile anywhere in between weekly and never. More often than weekly will start to interrupt certain fungi's life cycles and slow the process. But never turning it will also work, just more slowly.
Here is a nice guide on composting if you want to get into the nitty gritty.