I'm deciding what netbook computer to buy (probably ASUS Eee 1015E or ASUS X201E-DS02), but I want a solid state HD. What SSD would work to install in these computers? (500GB size is the max. I'd need.) I'd also like to know what case to buy when taking the HD out of the new computer, to make it into an external HD.
Any SSD will fit on a Notebook, is as simple as that.
Pretty much the same with your other question, any 2.5 external hard drive case will accommodate a notebook hard drive.
Both are very simple to switch.
You only need to be concern about either: transferring your Hard Drive to your SSD or having your OS/Programs/Data disks to install everything back.
When I did, I simply transferred everything then switched the drives.