It took me about 5 hours to do it and it was so incredibly simple.

Bought 500gb wd scorpio blue and external hd case.
Put it in external case then plug in via usb and install osx on it using the install dvd. (about an hour)
After the install it will ask if you want to transfer your existing file folders, i chose yes from another volume on the mbp. (220gb data took about 3 hours to transfer)
Take out 500gb from external case and install into mbp (takes about 5 mins)
Start it up and run software update (takes about an hour)

And thats it, i thought it would be hard but transferring everything before putting it into the mbp made things a lot easier. Times are not exact since i did other stuff while it was running but ball park figures.

If your on the fence, its very easy and all my stuff runs like it did before the swap just with a lot more space. Good luck and make sure you back up everything.

My next step is deciding what to use to back up my 500gb since all my externals are only 320gb.