double pane will keep you cooler and warmer less noise. I have the same company and re-did myself. For 8 windows around $250 for all several years ago. 1 st one will take you half day and after that two easy per day. There are also a company in Florida and I think Oregon that does the same thing for around $200 plus per window.
When i took mine apart the reason they leak was not enough mastic around the windows in the corners. So they leak, I use a product design for homes and it does seal well and then you seal it again with a high end sealant. I sure some one will chime in with the name of the company.