I don't have any experience with downloading free GPS updates, but the word "toolbar" chills my blood. Toolbars are the bane of my computer fixing life. My rule of thumb for people is NO TOOLBARS. I do use one for my Roboform Password Manager, but that's it.
If it was my Tom Tom, I would get the maps from the source to be sure you were safe. When we got one for our German family when they visit us, we paid a little extra up front for lifetime free map upgrades.
Hopefully someone will have some experience with these free GPS upgrades. Maybe they're fine, but if you decide to try it, get rid of that toolbar ASAP.