Hi. MXP is a pretty easy airport to navigate. At Alitalia peak atlantic arrival time 730am-830am it can be a bit of a disaster, but by the time the Delta 763 gets in it should be pretty no-hassle.

Correct, they will clear passport control, but will not need to clear customs, unless of course they decide to pick up their bags, which I really don't think is necessary. MXP is a hub airport and is pretty well versed at bag transfers.

There is a transit desk where they can check in if necessary, but Delta should issues boarding passes for the MXPPMO leg as well.

As far as I know there is essentially nothing near the airport.

If they are flying Delta BizE they should have access to an arrival lounge to hang in for the 4 hours. Also, if the entire ticket is a business class ticket (this is possible even though the Alitalia flight is all Y), then Alitalia will probably grant lounge access.

Hope this helps. They should have shot for the Alitalia JFKMXP flight on a 777...so much nicer the Delta's old 763.