I second Multisim, easy to learn and you can eventually take the design and put in in Ultiboard etc. If you are a student there are educational versions available that are cheap.

So basically what you are saying is that by adding the Ground-fill beneath the connector (and because of the skin effect preventing the signal entering the ground-plane) it will need to go to the edge of the ground-plane and back to find its optimal route (similar to a segmented plain causing to route via decoupling capacitors )