A/C

Would I still have to vacume it out and that sort of thing before re-charging?

If there is still pressure in the unit you would not need to pull a vacuum. You would want to purge the hose of any air with refrigerant as you screw the hose onto the unit...

the thing to know here, is that if you're charge is low, you have a leak somewhere. if you pull a vaccum, you will pull moisture into the system. you have to find that leak, or be ready to keep adding to your charge. it may work for a while, (depending on the size of the leak). when i leak test a system, i remove the remaining charge, pressure the system to about 250-300 psi. i use an inert gas, sush as carbon dioxide, or dry nitrogen, then go over the sealed system solder joints,with a solution of dishwashing liquid, & water. look for oil , this is often the sign of a leak. if you can find the leak, you have done the half the work, & often the most difficult half. although most leaks are repairable, some are not. i would suggest repairing it, ( if possible.)

I have to put quarters in mine and turn that little knob.

so do i, i just pay all mine at the end of the month