There is no loss when the lines are made up.....jesus
Yes, they come precharged...precharged for that particular condenser...a matching evaporator and a manufacturer specified amount of tubing between the two units. Some manufactures add enough for 15 foot of tubing some for 25....this charge still may need to be added to because of increased tubing length etc.... and it still must be checked and adjusted by a competant person because the factory charge may not be correct..especially if charged at the factory by a fat lazy american with no work ethic.... also checking the charge will also show any problems with the system itself....too little airflow, kinked tubing....
You need a professional to check out the equipment...too much or too little gas both can result in increased compressor wear.
refrigerant recovery..... look for the access ports on the outside unit...take a valve core remover...like you would use for a car or bicycle valve stem and loosen the core to where you hear a steady hissing......come back the next morning and push in on the stem....if it hisses just a little bit just remove the corer completely..do this on the big line to minimize the release of tell tale liquid refrigerant.
If you are going to attempt this yourself...good luck...you have not mentioned proper brazing techniques, leak testing...evacuation.....
and they call me corny................ ~:>