Has anyone replaced one of the slat windows in the aft on the 500
Yes, we had one crack due (perhaps) to a poorly placed bumper. Care should be taken to avoid the windows with bumpers or straps We had the glass shipped from Knysna ($$$$$$ and 
) to St Martine and had a local guy install it. Its not straight forward but does not require special tools other then a calking gun.
Thanks rwy, we got hit by a tender and crack the window but, we actually have a spare onboard. My biggest question is, it that a rubber seal or just sikaflex around the outside of the window?
Yes, he put spacers in to hold the window where he wanted it and used a number of tubes of sika flex (the UV stable, slow cure one) to build and smooth the gap. Once cured, he removed the spacers, filled the holes and applied a “finishing” coat of flex.