Hi JWS,
First, can you make sure the screen you are editing is the right one? You may still have the stock "Sales Orders" screen up (which is not editable) -- hover over the "Sales Orders" link and make sure it says that the corresponding screen is the one that you edited. If it's still pointing to the stock screen, you will have to change it to point to your new screen so that you see the changes.
If this part is fine, then the following steps should help.
The approach you're taking is to try and restrict viewing the entire grid. My suggestion is to create filters and restrict them based on the role. So, a filter that you place on the grid allows you to set a condition on the data that's displayed -- you can do this in step 4. You can either create or edit one of the existing filters, and add some conditions.
For your situation, I would recommend deleting all the existing filters, and creating two new filters. The two filters will be as follows:
Filter 1: Name it "All Sales Orders" -- you dont' need to put any filters on this (because this option will let you view every sales order there is), but in the "Edit" section, go to Step 2 and uncheck the "Dealer" option. By doing this, the dealer won't have access to this filter, but everyone else will.
Filter 2: Name it "My Sales Orders" -- for this, you will click on the dropdown beside "Choose from a list of available fields" and add a filter for the field "SalesRep". Your filter properties would be set to something like "equal to" "value from session" "User - Sales Rep Initial" (or whatever field in the Sales Order that corresponds with the role).
Let me know if that makes sense -- it's a bit confusing, so I apologize if I explained it poorly.
Naeem