Should I buy it? 87 300e won't pass emissions

[tjh]

A pre-test smog test here in California failed this car as a "gross polluter." HC's and NO were both *very* high.

Otherwise the car is in great physical shape inside and out (with a few nits to pick - blinker doesn't blink but signals illuminate, front left/rear right windows don't respond but will if relay is bypassed.)

Neighbor offered it to me for $500.

I don't know enough about emissions systems to know what could possibly make it fail so badly.

Any Tips?

What's a list of possible causes and any repair cost estimates?

Thanks in advance!
tjh