here is refrigerant... you dont need a license to buy 410a. You do have to have a license to buy R22 though... LOL
https://www.ebay.com/itm/R410a-refri...nd!43123!US!-1
Scale
https://www.ebay.com/itm/220-lbs-Ele...AAAOSw8HBZNh8D
The best bet is to evac the system, pull a vac and recharge to factory amount, over charing is worse that under charging! The split temp (temp between room air and discharge air) should be when properly charged between 18 and 22 degrees. Of course once the ducts lower in temp.
Self piercing valves arent the best in the whole world, but they work and have used them plenty of times!