We've also connected the S7200 PPI interface to some GP377R's. We're still using and old version of GP Pro (V7.01E) in the Device setup just select the S7200 PPI interface and you can get a pinout of the cable you have to make up on their website.
Yes - the small displays are RS232 and need a gender change plug and an interface plug. The larger displays are RS485/MPI and just need the interface plug.
Available from your dealer. I can get the part numbers if you need them.
I use a length of profibus cable and two profibus plugs with internal terminating resistors. This also works with the small displays.
Yes I have used AGP 3200 and 3300 connected via RS232/RS485 port. Software configurable port to enable RS485/MPI as markie suggests. The driver is selectable in GP ProEX. Proface even will send you the cable. As usual the HMI is the Master. Works and behaves very well.