The grinding may be your syncros. Usually the 3rd gear syncro goes in Hondas first.
As far as the clutch goes, if you don't have major mods, and you don't beat it the stock clutch should last more than 40k miles.
IMO an after market clutch is one of the best mods you can get. I'm getting an ACT.
Even if your clutch is still good, an after market one is still a great upgrade. After I drove my friends Si that had an ACT I feel in love. Theres just something about chirping third that did it for me
