what is the r134 capacity of this system? my ac is completely (and i mean completley) discharged and im going to recharge it soon and i need to know how much to buy.

it should be printed on the conversion sticker under the hood if its been converted, or it may have had r134a from the factory.

you could always call the dealer and ask them. those DIY cans are crappy becuase you'll be overfilling the system with oil since you still have all of the old oil in the system. you need the oil removed or just a charge of r134A. have a shop do it, you'll get the best result that way.

also the reason its all empty is because you have a leak, probably a bad O-ring, rubbed through line, leaking condenser, leaking evaporator, bad compressor seals, are all common problems.

its empty because i bought it from someone who was parting out their celica so i assume he didnt ship it with r134a in it

Also worth noting is the fact that refrigerant mixed with moisture produces an acid that will eat away at your seals and O-rings. A shop will evacuate the system and in the long run save you money.

also, you'll need to make sure you put the correct amount and correct type of oil in, yet another reason to take it to a shop.