Jeff,

First, not to worry about the filter, it was eliminated on the production line, as a cost saving measure, and it served no major purpose. It's not missing on your unit.

No, you normally do not need to replace the filter assembly, unless it's clogged with hard water deposits, or has a hole in it.

The spinach particles, is most likely a by product of 2 things,
Water temperature is not hot enough(needs to be 120 dgrs F. in the tub, on the first fill of the wash cycle).
Your detergent/rinse agent is probably "foaming" up during the rinse cycle.
Check your drain hose and system for possible clogs or restrictions.
On your unit, there should be approximately 1/4 in. of water left in the center of the pump housing at the end of the cycle.(it may slightly cover the 6 screws holding the pressure dome to the pump assembly).
You may want to try this,
Switch to a plain powderred detergent(no additives)and use the proper amount based on the water hardness, (available from the water supply company).
Run the hot water faucet at the kitchen sink, until hot, before starting the dishwasher.
Run it a few cycles using this method, and I'm sure you'll be a lot happier with the results.

Good Luck,
:) :) :)