Subzero 550 possible low side freon leak

[mitch55]

Subzero 550 with r134, 1997 model

I am a fairly handy person and have already repaired a few odds and ends on this fridge like the defrost heater but may be having an issue beyond my skillset. I did buy this fridge used but so far i have not had to mess the sealed system. 

The Issue

The other day i noticed the drip tray had overflowed and that the water in it had a oily texture to it. The water tray overflowing ithink was casued by the seal being kinked for the freezer. The only thing i can figure that would cause that oiliness is a slow freon leak(lowside?), inspecting the condenser it appears there is one spot with some green crust. So far the compressor does not seem to kick on anymore than usual and the freezer is still frozen when set at 6. 

Before i go down the path of getting a tech out here to look at it i would like some opinions on if there is anything else that could be causing the oil in the drip tray. I did do some searching and it seems its always the evap to go out in these, not the condensor.