Welcome to the forum!
The Train Collectors Association has a set of universally accepted grading standards for toy trains. You can view them here, and make an informed decision as to where in the standards your trains can be properly graded. http://www.tcamembers.org/standards/GradingStandards.pdf
An extensive explanation of the standards is available here.
http://www.tcamembers.org/standards/TCA%20Post-war%20Trains%20Grading%20Guide.pdf

The best way to get an education on what prices are realized in sales, is to check online auction sites. Look up the numbers on the side of your trains. The transformer looks like it is a ZW model. Study very carefully the condition of items sold. Your first step would be to clean the items as best as possible of dirt and grime. An old toothbrush and a drop of dish detergent will get your trains clean. Be very careful around decals, as you do not want to destroy them.
If there are any hobby shops in your area, take your cleaned trains there and ask them for a value. Any toy train shows in your area should be attended to get a feel of what is sold, at what condition, and for what price. You may be able to sell them at a show also. Your hobby dealer may have info on upcoming shows in your area.

Educate yourself so that you get a fair price for your trains, and also sell them as quickly as possible for the proper price.

Larry