Toyota Repair: AC, r12 freon, side ports

Question
I have a 1989 Toyota 4x4 pick up truck.  The AC has not worked for years.  It does not blow cool ar.  I have bought a conversion kit.  The watch glass on top of the dryer does not seem to have anything in it.  I know that I need to have the old R12 Freon removed by a shop.  Might the system already empty?  In addition, where are the low side and high side ports located.  To me it looks that they are located next to each other on top of the compressor.  Am I correct?  According to the kit directions, the conversion looks pretty straight forward.  Basically, I need to screw on the 2 adapters and then fill the system.  Is there anything that I need to be especially careful of?

Thank you,

Howard Friner

Answer
There are also service valves located on the hi and lo pressure lines, the high side valve is located near the receiver drier and the low side valve is located near the firewall, you can check for any freon in the system by depressing the valve stem of either side to see if any freon escapes, if it is empty go ahead and install the conversionkit and put in the freon and see how it goes, there may be a leak somewhere in the system but only time will tell.