Usually older burners don't have correct strategies to burn high speed media, so it's advisable update firmware if an unpdate is available.
If the burner is really old maybe it's better to buy a new one because are not more supported and new firmwares are not available. If a burner don't find a media in its firmware, often burn it at lowest speed available. Burning a 16x media at low speed often give bad results (too many errors on the disc).
Take a look here to find if it's available a new firmware for your dvire.
For what I know, there is not a special procedure to update firmware: simply run the flasher. But I don't have a NEC, so I don't know if there are some special precautions to follow different from any pther firmware update.
The usual precautions are the following:
1) Be sure to select a firmware for your burner, and not one for a different model
2) Be sure to flash the correct one if you have more than a drive connected (for example a dvd rom or a cd burner).
3) Avoid power interruptions during the flashing (for example, don't flash a drive in a stormy weather): a power interruption could make a drive unusable.