I believe you should be hooking up your RA trim servo sensor wires to your GEA24 if you want to have trim position gauges on your G3X. See Figure 26-2.3 on page 26-6 of the G3X Install Manual, revision U. So the three sensor wires, green, orange, & blue (stripes), should match up with the pin numbers on this diagram, pins 18,19, and 20 for elevator trim.
I like your idea of trying to get someone with wiring experience to help you finish this job, you'll learn a lot observing someone who has done this before. Not to mention this person having all the right tools and other odd and ends! But you can certainly do it yourself and learn a whole lot along the way. You might make a mistake here or there, but troubleshooting your mistakes is also a learning experience! One of the most common errors is miss-pinning, i.e, inserting a wire/pin in the wrong pin position. Triple check all of your pins before finishing a connector! Get a good magnifying glass! Don't assume numbers go from left to right! Sometimes it's right to left. Good luck with the project and post any other questions you might have.
Edit: in re-reading your post, I realize now that you have a GSU73 setup. So, yes, you are correct with pins 47, 67 and XX. With "XX" being a suitable signal ground pin on the GSU73, such as pins #18 and #37 on the same connector. You may have to use another signal ground from another sensor and splice into it if there are not enough signal ground pins in the connector. Correct figure number is 26-3.2, page 26-9. Sorry for the confusion.