Switch to a new Gmail email address without losing account data? Suppose I have some cheesy gmail address that is inappropriate for putting on resumes and such.  What is the easiest way to change it, while retaining my documents in google docs, as well as photos, google music purchases and playlists, and so on?  

Does Google have any provision for this, or are you supposed to start completely from scratch and painfully transfer all the data manually (as well as cancel music subscriptions and restart, etc)?
Your email is the key identity for Google account and you are right about starting all over again, if you delete it. See what happens to my google acct if I delete the gmail service?
If your concern is only to have a respectable mail address for correspondence you can use an email alias,for which you can't use Gmail app but alternative explained here Sending email from an alias using Gmail app