Think about sightlines from both sides
Look at what someone outside can see when the garage is lit after dark, as well as the daylight you want inside. A small sample does not show the entire door in context. Discuss the window location using an elevation or product drawing.
Check the selected configuration
Window designs and glazing choices vary by collection. Ask the supplier to identify the exact combination in the quote and confirm any relevant performance documentation for that choice. A photograph of a similar door is useful inspiration but does not establish the ordered specification.
Keep future repairs practical
Retain the model, glass description and layout information with the installation records. These details can help when discussing a damaged pane or section later. Ask about cleaning and care before ordering, particularly where access to the inside face may be restricted by stored belongings.
Your questions
Is frosted glass completely private at night?
Privacy depends on the glazing and lighting. Review the product description and a representative sample rather than assuming every obscured option hides silhouettes equally.
Can windows be added to any existing door?
Do not assume that. Have the manufacturer’s options and the current assembly reviewed before cutting or changing a section.