Your 3GB drives are excellent... for doorstops and paperweights (but are too small to use as boat anchors).
They are well past their service life, and will likely fail very soon. Not only that, they will have horrendous performance compared to modern drives (especially ones which use perpendicular recording). Send them off for recycling. Seriously. I mean it.
You seem like you have very little experience with RAID. There's no shame in this, but RAID administration is part black magic, part science, part experience, and part voodoo. For you, I would recommend a Drobo. If you're going to boot off it, you can use a Drobo S with e-SATA if you're using Windows, or any Drobo for a Mac (since booting a Mac from USB or FireWire is fully supported; FW800 is best in this case).
Put the drives into the Drobo, configure it as NTFS (Windows) or HFS+ (Mac) with an 8 or 16 TB virtual array size (to allow for upsizing in the future up to the selected virtual size without redoing it all), aaaaaand... you're done. If one fails, it tells you (both in software and on the unit's LEDs), and you pop it out and replace it with any drive that's the same size or bigger -- without powering down. You can expand the RAID with larger drives by replacing them one at a time while the unit is powered on and online (the data is still accessible for read and write during upsizing!).
If you absolutely insist on doing it yourself, get a high-quality RAID adapter. 3Ware, Adaptec, Areca, and Intel are good examples of quality. Poor-quality adapters (Promise, Silicon Image, Realtek, etc) generally do the heavy lifting in the driver, resulting in performance issues. Use RAID5. Make sure the solution you're examining will alert you to failed drives, or else you might never know until the second drive dies (causing the loss of all data on the array).