Hi Chad,
In case you're not aware, Mark Basch is the top NSX mechanic in the country - and fortunately for you, he's right in your neighborhood (602-244-8010).
He has posted his advice about what to do with a snap ring transmission, and it is copied to a topic in NSXprime - click
here.
Briefly, this is a summary of his advice:
1. Familiarize yourself with the symptoms of an actual failure of the snap ring (the gear shift knob will feel loose, etc).
2. If you experience those symptoms, then
don't keep driving on it. Take it in to get fixed, and you will probably only have to replace the snap ring and transmission case, not the whole transmission.
3. If you don't experience those symptoms, you can either (a) have those two parts replaced anyway, for a parts cost around $700 and labor cost around $1000, or (b) wait until you need transmission work anyway (e.g. clutch replacement) and have the parts replaced at that time, so you save the labor cost by not doing it just to do the snap ring fix.