I wouldn't replace the reservoir itself just yet, most likely it is the hose. Remember, where there is a rubber hose, there will come the leak. You can probably buy new hose at your local AutoZone or something. A lot less costly than replacing the whole reservoir, unless you can clearly see that the coolant reservoir has a crack in it. Be sure to find the source of the leak first. I don't think that you will have any trouble taking a seven hour drive, be sure to have a bottle of coolant with you though, just in case. If the car isn't getting enough coolant, it will let you know about that via the panel lights.

Hope this helps

Max