that's the tutorial for setting up the p2pool node. The more difficult part I'd say is installing the ATI driver and the APP SDK for OpenCL mining.

Do the driver and SDK installing from this tutorial https://bitcointalk.org/index.php?topic=9239.0 since your using cgminer you don't need the pythonopencl part
and the bitcoind and p2pool configuration from your tut

It should work with every linux distro but ubuntu is the handiest of beginners. So you should go with that. There are plenty of tutorial on how to install ubuntu and its really easy to use. If ubuntu runs and your GPU is working the rest isn't much of a problem then.

You would need a few gigahashes but compared to p2pool solo mining has no pros and one con: higher variance

I think the only decision you have to make is wheather you should use a traditional pool or p2pool.

The biggest advantage centralized pools have is the low variance. For example you have the hashing power to generate 1BTC per day which means 30BTC per month. A tradiotional pool will pay you very close to 1BTC every day so you have a steady payout.

At p2pool on some days you get nothing on someday 1.5BTC and one other days 2BTC but if you mine for one month you will get 31BTC.

Another advantage of p2pool is that it's decentralized which is probably healthier for the bitcoin network but also it can't be shut down, hacked and theres no operator who could steal bitcoins from you if he wanted to. There's no single point of failure.

I think that your not going to run your rig for only a few days so the variance shouldn't be a problem. I mean why would you care if you get nothing today but 2BTC instead of 1BTC tomorrow when your running your rig for several months anyways. That's why I'd suggest to go with p2pool but it's your decision.

depends

Where do you want to point your hashing power at?

If you want to mine solo you will need to run a local bitcoin client (if your hashing power is too low thats probably not an option)

If you want to mine in a traditional centralized pool you have all you need.

If you want to mine in p2pool you have to run your own local bitcoin client and the p2pool client.

centralized pools have the advantage of low variance in your payouts but with more hashing power in a few big centralized pools the bitcoin network itself gets more centralized which CAN cause serious problems to the whole network.

Its a little bit harder to set up a p2pool node (there are many good tutorials). But with using p2pool you help to get bitcoin more decentralized and therefore probably stronger.
Another advantage is that you don't pay any fees unlike with most centralized pools but you will have a higher variance in payouts.

I'd suggest that you try p2pool I would provide help to set it up if needed. And if the variance is too high for you (but in total you earn more) you can later switch to a traditional pool in a few seconds.

Im a physics student from germany and im dealing with bitcoins for almost one year now.

It's a really interesting idea to me and I think it has a lot of potential. I've been reading the forum for a long time already and finally registered myself now to take part in a few of these interesting discussions taking place here. I wanted to post my personal experience with p2pool in a thread but guess I need to stay here for a while first :

So hello2everyone