Is the evaporator/freezer fan running?
it should be on whenever the compressor is on.

Is the condenser/compressor fan running?

Are the condenser coils clean?

Is the compressor running?
You can usually hear it but also should be able to feel it vibrating.

If it is on, is it on all the time except when it goes into a defrost cycle?

If it is on all the time you will have to check the evaporator/freezer coils.

If they are heavily frosted/iced over it is probably a defrost problem.
When you checked the defrost parts, did you force a defrost cycle?
If yes and the defrost heater came on then the problem is most likely with the defrost timer.

If they only have frost in one area (usually where the freon enters the coils), then it is probably a sealed system problem.

If the compressor does run and seem to cycle properly then it is probably a control problem.

If the compressor short cycles then it may be a start device or a compressor problem.

[COLOR="Blue"]Is there anything else I can try before calling in a repair man[/COLOR]
Not if you are sure it is a sealed system problem.

To help ensure that you have made the correct diagnosis see the below, take a look at the example pictures about ha;lf way down the page.
http://www.applianceaid.com/ref...ator-not-cold-enough.php

A sealed system problem is an expensive repair.
Often it makes more sense to put the dollars towards a new unit.

I would check the warranty on the unit as often the sealed system has a longer warranty period.