There isn’t a specific guide on FoH/Mon digital splits. The first things to do are patching your signals in the I/O Screen and setting the clock appropriately.
The Factory template FoH and Mon shows will give you a good starting point with sensible bus config and strip layout for each.
In your configuration I would recommend using the DM48 as the master clock, so set this to ‘Internal’ in its Audio Sync screen, and set the DM0 to sync from the I/O Port fitted with gigaACE.
Patch tielines from your DM48 input sockets to the gigaACE I/O Port, this will send all inputs, straight off the preamp, to the FoH system. Do not patch Input Direct Outs for the split, as these will be affected by Digital Trim.
On the FoH system, patch the gigaACE I/O Port inputs to your Input channels. You might also want to patch your Mixes to the gigaACE I/O Port outputs, to send back to the DM48 (and patch to physical outputs there, using tielines again).
Once the gains are set, switch the Mon console to ‘Digital Trim on Surface’ so any gain change acts on the digital trim and doesn’t affect levels at FoH.
There’s many more tricks, for example for routing Talkback or using Ext In to PAFL for comms, but the above should point you in the right direction.
