It's going to get very wet inside!
i have done several brand new conny's where the glazers have 'cleaned' the glass and i have to say they are
usually problematic.
depending on what they used and how much silicone they have left behind will determine how much scrubbing you need to do, also some (if not all) fit the windows and use some sort of oil - this can run on the first clean as the water washes it out.
i have found lightly spraying with a mild tfr solution and giving everything a 'double rince' leaves it really good.
-but inspect well as silicone residue will require hand scrubbing/scraping
Darran