Hey guys, just to add a little info that is hopefully useful to others, I took some pictures after going through this adjustment.
I'm using a 10x probe. 100x might be better but I don't know the circuit. I don't like loading down oscillators which could shift the frequency I'm trying to adjust. This is a cheap but very good $120 or so frequency counter from China and is being fed around the back with a 10MHz external reference (Trimble Thunderbolt GPSDO). This version is good out to like 6GHz. Not a sales pitch, but my HP units can't beat it for portability.
I needed to use a pretty skinny probe to reach back to the PCB. There's a hole for the tip of the probe to slip into if you can reach it (I couldn't with the original probe I tried). Definitely ground your probe shield somewhere. I'm clipped to a 1/4" jack for paddles. The little hole right next to it has the trimmer pot/cap (can't quite tell from out here). I used a ceramic blade adjustment tool, but plastic would likely be better only due to the fact that it's a tight fit and the ceramic isn't exactly bendy. Plastic probably would get around the scope probe a little easier -at least with mine.
My gut feeling is to recommend some minimum warmup time like 15-20 minutes before doing this adjustment. I turned it on and spent maybe 5 minutes looking around for the counter (lost the darn thing on the workbench -it's small!) I've already drifted about 0.12 Hz, but this kind of thing isn't exactly a precision oscillator with double ovens and all that. That said, I'm optimistic that my clock won't be terrible now.