For a new hard drive try Newegg.com http://www.newegg.com/Store/SubCategory.aspx?SubCategory=380&name=Laptop-Hard-Dr ives&Order=PRICE
Or OWC for regular hard drives and SSDs http://eshop.macsales.com/shop/hard-drives/2.5-Notebook/
Here are video instructions on replacing the hard drive on the White Unibody http://eshop.macsales.com/installvideos/macbook_13_09_unibody_hd/
To transfer your current hard drive I like the free application SuperDuper. It makes a bootable copy of everything on your hard drive http://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html You'll need a cheap SATA external hard drive case. Put the new drive in the case then format and partition the new drive and clone your old drive to the new one. Check that it's set up right by booting up from the external drive. Then replace your old hard drive with the new one and put your old one in the external case.
Here's a cheap SATA external hard drive case on Amazon http://www.amazon.com/Vantec-NexStar-2-5-Inch-External-Enclosure/dp/B002JQNXZC/r ef=pd_cp_pc_0
If you don’t have the tools to open up the MacBook OWC has a set for $5