Thank you! I was able to easily change the hard drive of my daughter's Macbook. Didn't need the spudger at any point though, which is good as only had makeshift options available for that.
(Wasn't able to update the OS on same drive as it didn't show as an option in OS installation even after trying Erase/Partition steps using the Utility, as mentioned at several places online. But did finally manage to clone from Time Machine backup and then update the OS onto that.)