AC went "poof"

[kensousa]

So I'm learning (the hard way) about air conditioning.
I picked up a '71 Cheyenne that was a factory AC truck.
It was missing a compressor and the PO had taken most of the other parts off and handed them to me.
So with some pictures from this board, and a lot of trial and error, I was able to find and mount a compressor, re-mounted the condensor, and re-mounted the hoses, brackets, etc.
I'm pretty sure that I had everything hooked up correctly......

So I picked up one of the home conversion kits to change it from R12 to R134.
Put the low pressure adaptor on the low pressure side.
Fired up the truck.
I'm missing a switch that fires up the compressor, so I put a hot lead jumper to the compressor.
The compressor clutch pulled in.
Everything looked ok.
I put one can of the R134 into the low pressure side.
Pressure rose to 10 ish PSI.
I put a second can of the R134 in.
Pressure rose to 15 ish PSI.
I didn't want to put any more in, so I sat there and let the truck run (with compressor clutch engaged) for a bit.
2 to 3 minutes later, I hear this fairly loud "Boom" and see oil and coolant leaking out of the evaporator both from the firewall side and inside the cab.
Not dramatic leaks, but definitely stuff "oozing" out.
I pulled the inside duct work and the evaporator looks ok, at least with a cursory look.
Other than the obvious advice of "take it to someone who knows what the hell they're doing", can you guys give me some tips on what to look at next?
I'm trying to avoid pulling everything off of the firewall and pulling the evaporator out, but wonder if I haven't blown something up that's serious in there.
thanks