Welcome to the ownership club. The NSX is remarkably durable, especially if it has not been messed with. My 2000 NSX has only failed to start on three occasions, twice because the maintenance free batteries did the little sudden death dance after 7 years of use and most recently the main EFI relay failed after 21 years.
Accelerating electronic module failures are a reality for most cars designed and built through the '80s and '90s. The speaker amplifiers, head unit and the climate control unit appear to be the modules that suffer capacitor failure earliest. However, these are non mission critical functions that are just an annoyance if they fail. The main EFI relay is more than just an annoyance because it leaves you dead in the water when it fails and it can fail without any warning signs. OEM replacement relays are not very expensive and aftermarket relays are inexpensive:
1998 ACURA NSX 3.2L V6 Fuel Injection Relay | RockAuto
Relay replacement is not hard to do; but, it is not something that you can do without tools so if it fails in the parking lot at the grocery store you are in for a tow job. Because main EFI relay failures are such a common occurrence on Honda products of this vintage (not just the NSX) I would replace pre emotively if it is still the original relay.
Check the battery post cable clamps on your car. Honda clamps are notoriously flimsy and get overtightened leading to tearing of the clamp body and subsequent failure to grip the post. This causes a bad electrical connection leading to all kinds of weird intermittent electrical problems including error codes on the electric power steering and failure to start. Visual inspection and trying to twist the clamp on the post will tell you whether you have a problem.
The NSX (and a lot of other Honda products) use these stupid little plastic stoppers on the clutch and brake pedals to actuate the brake and clutch switches. They age, crack and fall out which results in various problems. The most egregious failure is the upper clutch switch stopper because when it falls out it will prevent the car from starting and it is murderously difficult to insert a new stopper. Purchase and carry spare stoppers in the trunk. You can replace on a pre emptive basis if you choose; however, the upper clutch switch location is such a hassle that I just keep a length of wire in the trunk to jump the starter solenoid if my stopper should fall out in some inconvenient location.
Most important are the maintenance records on the mechanical parts. Look for the dates on the following:
the timing belt was replaced,
was the water pump replaced when the timing belt was last replaced,
transmission fluid changed,
coolant last flushed, and
clutch and brake system flushed.
Since you live in a hot climate, have the engine coolant hoses been replaced? Heat accelerates the ageing of rubber components.
If the major maintenance items are up to date, then you can consider doing the stereo system and CCU capacitor replacements on a pre emptive basis. I would make sure the major maintenance items are up to date before doing anything that is less critical such as the stereo and CCU. Electronic module repair is done by Brian K at NSX Erepair
Your NSX is now approaching vintage / classic sports car status. You may find it increasingly difficult to have it serviced, particularly by dealerships where the factory trained NSX techs have probably all retired. Get a copy of the factory service manual for your model year so that you can do some of your own troubleshooting. I personally think hard copies are best; but, there are links to free .pdf versions. The only problem is that some of the .pdf versions are missing important pages. A more difficult to find document is the Electrical Trouble Shooting Manual. However, that document can be a life saver if the car develops any electrical gremlins.
An OBDII scanner can be a useful diagnostic tool. However, if you don't already have one wait to purchase one when the car actually generates an error code. My car (a 2000 MYr) has never generated an error code.