Ok I got burned for this once before. So I will be careful. I don't see what mother board you are using. If it's an ABIT is7 or ic7. They show the cpu temp higher than other boards do. 55 is only a little high. I wouldn't worry too much about it.
These specs are here so I don't have to repeat them. P4 2.4c @ 3.0 ASUS P4P800 dx Geil pc4000 2.5,3,3,6 250FSB 1:1 Radeon 9500 non-pro 2 Maxtor 60gig 7200rpm 8mb cach in raid 0 SB Audigy 2
I have my 2.4c running at 2.9ghz using ASUS's AI overclocking utility. It is about 27C idle and 43C loaded. 3.0ghz doesnt sound like you are pushing too far - heard of many people at 3.2c without problems.