Using aog with Trimble hardware

Would it be possible to use AOG but with a Trimble nav 2 and ag25? Or whatelse would be necessary other than screen?

Not really.

You can use your ag25 antenna I guess, but its used value is ~$800 and an AOG style replacement is $55-120. Just keep the antenna with the monitor and sell them as a package.

You can’t use the NavII at all. You can make your own pcb/box that plugs in at the 40 pin connector and does all the same things AOG style. The AOG box is around $350 USD and the NavII used value is around $2000.