The only real question I would bring up is how much oil to add. Since there isn't any history one can not know how many times freon was added only to have freon and oil leak out. I would probably add a little more oil than the component guide would say. I imagine this would be around 1.5-2.0 oz.
Flushing all the system to remove all the oil would require removing the expansion valve. The expansion valve is outside the evap case and not that difficult. Removing the oil would allow a total refill which is the only real way to know. Unless you are real sure of your flush technique I would just add an extra oz.