which internal harddrive option is best for a macbook pro mainly used for running logic 8?
i will also use other music software, samplers, synths etc.- is 5400rpm good enough or should i choose 7200rpm option?
how should drives be set up? external too?
please help me with this - i'm relly confused

well 7200 RPM is best and Logic 8 will have samples and audio content that it will be accessing from your drive if you plan on using any of it's software instruments. I don't reccomend it but I realize that there are times when you may need to record onto your internal drive and that people actually do. It's not very safe but if you do actually have to record onto your internal hard drive it's definitely best to have a 7200 RPM drive. I would reccomend getting an external drive for all your projects though and even a backup for that external drive to keep your data safe.