Thanks Spec R for the reply.

The thermostat is only $24 at the dealer so I'm going to just use the OEM part and have it changed out.

If I have the dealer change out the thermostat I might see how much they will charge to take a look at the car and determine what the black gunk is. I'm trying to decide what to actually do becaue I'm might just get the 90K done on the car sometime this year, so I can have the spark plugs changed and have everything done all at once.

I got an oil change about 1 month before the smog test.

Any additional comments regading my situation from Spec R or anyone else?