I wanted to condense all the questions I still could use some help with.

1) If there is no leak, how does the refrigerant get low?

2)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?

3) What oil is used? PAG or Ester? If PAG, which viscosity (low,med,high)?

4) I had this in mind to say to the service rep "I believe there is a leak in the High side pressure hose, there is some oil residue on it, but would appreciate you checking out the other components and giving me an estimate for repairs". That sound reasonable without them thinking they can easily take advantage of me and also any guides on price of the high pressure hose I think might need to be replaced.