The only drawbacks were that it was due for the 30,000 mile major service
Which should cost around $700
and the rear tires were bald and in need of replacement
plus another $400 for the great-handling OEM tires.
how does reliability and scheduled maintenance look like for a 1993 NSX?
Scheduled maintenance is similar to most other cars. You can look up the schedule and typical costs in the FAQ here.
The NSX is a very reliable car, but things do occasionally break down. A clutch replacement can run $2K (clutches last anywhere from 20K to 100K miles, depending mostly on how it's used). Air conditioning repairs can also be expensive, $2K or more.