Duane
We are US citizens who relocated to Montenegro and have been here 2 years. A few answers.
From what I researched, the main ways to get legal residency is either to 1) buy a home or 2) open a business. Both give you the option to request legal residency. We used a local legal service in our area to navigate the process. Personally, I think it is a good option if you don't speak the language and are not familiar with the process. Feel free to send me private message if you want some referrals. About cars.. we have not purchased a car, but when we considered it, we were told it is fairly straight forward. I believe it will be similar to the US in that you buy the car, transfer ownership, and make sure you buy the legally required insurance. There is an additional insurance to be able to drive out of the country, usually referred to as a "green card". If I am wrong on any of the car information, I am sure some more experienced expat members can help.
Montenegro is a beautiful country, and the people have been very welcoming. I usually recommend folks visit before making a commitment to stay. US citizens can stay up to 90 days without any special visa's. A long stay is a nice way to get to know the country and get concrete answers to the many questions that will come up. I would recommend visiting March-May or Sept-Nov. That is basically before and after tourist high season. There is usually good weather and costs of flights and accommodation would be lower than in summer.
Hope this helps a bit on your research.