You can try the Auto OC feature, its really your call.
But I would advise learning to do it properly through the bios for the reasons I mentioned above.
If you do decide to learn to do it manually, as well as doing plenty of research of the OCing subject itself, find as much info as you can about your hardware before you start.
1) Make sure you know how to reset your bios in case it refuses to post or does not automatically reset in this case. (If your board has such a feature)
2) Learn your CPU and Motherboard limits (Temprature & Voltage Ranges)
You'll need to know the default settings for Voltages as well as safe and Danger Zones for Voltage and Temps.
3) The specs. RAM timings Voltages etc.
4) keep in mind when OCing, the RAM is the easiest thing to fry. try to keep it at or below its rated specs.
--In fact, knowing these things would be quite beneficial, even if you start of with the "Auto OC' tools.
Because you can use the Auto OC feature as a base of where to start. Then lower Voltages etc. from there.
As far as your GPU goes, personally I find the ATI CCC Overdrive just fine.
What you can try if your unsure where to start is the "Auto Tune" Funtion, as seen in the snip below.
This will give a rough idea of where to start.
Once it gives the results, I would back off the Core and MEM just a bit.
Remember to "Test Custom Clocks" as well, if you make your own, and watch the Temps.
I make a Profile called GPU OC, that includes just the Overdrive section.
And another for default speeds in the same manner.
This way, when I go to play a graphic intesive games and want that little extra, I just enable my "GPU OC" profile and go at it.
When done, and just web brosing for example, I restore the default speeds.
If I remember correctly, the 4850 isn't a great Overclocker.
So don't expect a huge boost. In fact, most cards that do OC well won't give a major improvment, but it does help a little.
Hope this helps.