yes you can replace gasket seals and it will be a fraction of cost rather than replace with new window,firstly does your gasket come out of window without taking panes out,try and pull it out with a screwdiver,if it comes out buy some wedge gasket the same size and replace,if it dosnt come out its e gasket and you will have to take panes out to replace.hope this helps
shaun www.sdwupvcrepair.co.uk
April 2008