From my understandings with what I went through, the Insurance Company will determine a book value that they feel is fair and offer you that amount. This amount is based on your vehicles book value, condition, mileage, options and even aftermarket parts or recent work may also be a small factor in determining your Explorers value. If you feel they are trying to lowball you, you do not have to accept their first offer and you can negotiate with them. In my situation I was being lowballed over the value of my vehicle and fought with them for over a month to reach a settlement, which I thought was fair. Try to find out the NADA (National Auto Dealers Association) value of your Explorer, which is value the Insurance Company should be using and this may give you an idea of what to expect. Granted I am in now way an expert and this was just in my experience and may be different in your state, best of luck.
If your Explorer is totaled you can buy it back for a small amount off the settlement offer, which is what they would expect to get for it from a salvage yard. In which case you can have it repaired, part it out or keep it for parts. When my Explorer was hit, it was all cosmetic damage and was still very mechanical sound. I drove it around until it died and used the ins. check to pay off bills.
In regards to the rental, it should be covered for the duration of time your Jeep is in the shop if by chance it is going to get repaired or only a short period of time if they do total it. And will probably only for a small economy car. As somebody already mentioned a rental will only be possible if you are over 21.