Some chips are better at overclocking than others, I can't remember whether the 366 was good or bad for that. But a bit of info:
When chips are manufactured, they come off the same assembly line (more or less), and tested for max frequency. Sometimes a batch of chips will be capable of handling much higher MHz - than what is stamped on it. So these chips hit the market as, the classic example - Celeron 300A which are easily overclockable to 450MHz.
The celeron 366 is designed for running on a 66MHz bus, with a multiplier of 5.5 (5.5x66=366). If you wanted to get more MHz, you increase the bus speed (the multiplier is locked). Ideally, if you could run it at 550MHz using a 100MHz bus setting, your PCI bus would still be running at 33.3MHz. If 100MHz didn't work (unlikely it will) 83MHz, or maybe 75MHz, but you are overclocking the PCI bus at this point, and may or may not experience problems.
Also, ease or difficulty depends a lot on your motherboard, a lot of boards are using some sortof soft menu interface, through the BIOS instead of using jumpers. So this can speed up the experiments.
With a 366, I don't think the extra 91MHz is going to do much for you, messing around with the PCI bus speed is not something I would feel safe doing when trying to record audio. There are already more than enough ways of creating errors with DAW's.
If it's working fine for you now, don't bother. Better to buy a Celeron 600MHz, they are cheap enough. Or wait until you really need the extra horsepower and upgrade at that point as chip prices always(usually)drop.
.....good luck