refrigerant and oil questions

[ARenko]

I need to disconnect a couple refrigerant lines in order to replace my heater core on a 2008 Nissan Frontier. I'll have a shop recover the refrigerant, but plan to recharge myself. I have a few questions...

1. I assume the recovery process removes some oil - do the recovery machines measure this?
2. I assume recovery is like a large leak, for which my factory service manual says to add in 1 oz of oil at recharge. If I don't get a measurement from the shop should I just add the 1 oz and call it good?
3. I have the Nissan compressor oil, but I notice many refrigerants at the auto stores contain oil. Is there a brand of refrigerant that's readily available in the stores that does not have oil added to it?
4. If I do end up with a refrigerant with oil, I assume I don't need to add any additional oil (the 1 oz I mention above) to the system, correct? I'm sure the oil in the refrigerant is compatible, and it's only a small amount of the total oil capacity, but is there anything I need to be aware of?

Thanks for your help.

[Cusser]

My comments below in Capitals.

I need to disconnect a couple refrigerant lines in order to replace my heater core on a 2008 Nissan Frontier. I'll have a shop recover the refrigerant, but plan to recharge myself. I have a few questions...

1. I assume the recovery process removes some oil - do the recovery machines measure this?
NEGLIGIBLE

2. I assume recovery is like a large leak, for which my factory service manual says to add in 1 oz of oil at recharge. If I don't get a measurement from the shop should I just add the 1 oz and call it good?
DOUBT THAT'S NECESSARY, BUT 1 OZ. OIL WOULDN'T HURT.

3. I have the Nissan compressor oil, but I notice many refrigerants at the auto stores contain oil. Is there a brand of refrigerant that's readily available in the stores that does not have oil added to it?
LOTS OF R134a IS AVAILABLE WITHOUT ANY OIL, AND LESS EXPENSIVE TOO. I'VE SEEN PLAIN OLD R134a AT WALMART RECENTLY FOR UNDER $5 A CAN. WARNING: MANY CANS THAT CONTAIN OIL ALSO CONTAIN A SEALER - NEVER ADD ANY SEALER OR REFRIGERANT WITH SEALER !!! NOTICE THE BOLD !
4. If I do end up with a refrigerant with oil, I assume I don't need to add any additional oil (the 1 oz I mention above) to the system, correct? I'm sure the oil in the refrigerant is compatible, and it's only a small amount of the total oil capacity, but is there anything I need to be aware of?
SEE #3

Thanks for your help.