Harry is correct, the *unit* not the door must be replaced.
I would get estimates from SEVERAL glass companies. I've been in the
glass business for 25 yrs and the markup is outrageous. Glass shops are
very competitive with their prices, shop around.
Also make sure to ask about the warranty as far as the seal failing.
Some companies give a lifetime warranty because the glue used on todays
units is VERY good and hardly ever fails.