Also,

When purchasing the refrigerant, should I opt for one that is just refrigerant or one that refrigerant and includes oil? What about one that includes refrigerant, oil, and leak sealer? (I did see in another post a user with bad results with leak sealer so I'm skiddish of it already)

I don't understand what the oil is really and if there are any pitfalls to using leak sealer so any information would help immensely.

Also, what pressure should I recharge it to?