Questions about 477dw PageWide Pro

Need the printer every day, except during holidays. There was no problem with the ink even after three weeks of holidays in the summer ...

There is only one "scan module" in this model.
When you insert the sheets through the feed tray, the sheets are "pulled" over the scan module. This remains fixed in the start position (usually) on the far left under the glass.
When you place the sheets on the scanner glass, it is not the sheets but the scan module that is pulled under the glass (and thus under the sheets) and the data is read in

It is very difficult to see in the pictures, but the printer with dwt has an extra paper tray (labelled 3). It almost looks like a reflection of the top tray in the pictures.