I'll chime in since I just installed the GROM v-line last week in my 2005 LC. I was doing the cabin air filter mod and a few other things all at once while I had the tools out and the glovebox open, but if only installing the GROM and if you spend a little time in advance reading the instructions, and ideally have a factory service manual or Youtube video of how to remove the head/nav unit and glovebox, it's probably less than an hour of actual work.
Feel free to PM me for the relevant pages from the service manual, and if you have any specific questions. Specifically related to the GROM install only, here's what I did:
1. Disconnect negative battery cable, drop glovebox door and remove inner panel with airbag sensor and glovebox light.
2. Remove vertical vent panels on each side of nav unit
3. Remove 4 screws securing nav unit, let unit rest loosely
4. Install GROM wiring harnesses on back of nav unit, route wires to glovebox
5. Install GPS sensor on top of dash at far right, route wire down felt door trim to glovebox
6. Reinstall upper glovebox liner and glovebox, leave open
7. Plug harnesses into GROM box, USB extension into upper USB port, plug USB keyboard into lower USB port
8. Reinstall head unit and 4 mounting screws
9. Reconnect negative battery cable and start engine, and (if your antenna works) press antenna up button to fully extend antenna/reset antenna memory
10. Let GROM power up, connect to wifi, download and install software and firmware updates, follow written setup instructions to install Google Play store and other desired apps/extensions, ensure everything working correctly
11. Reinstall vertical vent panels on each side of nav unit, disconnect USB keyboard, close glovebox, have a beer.
So far, it's a huge improvement. The only glitch I have noticed is occasionally (maybe 10% of the time) I will get lines of static instead of the Carplay UI - I just press FM and then back to Disc and it has reset/resolved every time.
Hope it's helpful!