You can reseal your self . Clean all the old gunk from the channel ,i lay a couple of strips of 3M caulking ,the black type ,first . Set the window with the gasket in place ,starting at a bottom corner ,and pull the gasket over the lip . Some like to use a cord inside of the gasket to pull it over the lip but i have a hook tool to do this . Once the gasket is locked down ,carefully push down
Around the edges of the glass to seat it . Then you will need windower sealer ,caulking in the tube type ,insert the tip under the rubber in the channel and fill it up . You will also need to caulk between the glass and the gasket the same way