Hey, you have taught yourself in the past just like you mentioned. And you should give yourself a pat in the back for whatever success you have achieved in learning. Why need a teacher now? People are relying on their own ingenuity with the help of technology. Maybe you can save yourself the hassle if you stick to what you have been accustomed to.
Here's a helpful hint...Ask a teacher what 'voicing' is... if they stare at you blankly - SOD THEM!!!
'Voicing' is the ability to make the top note in a chord sound a little more than the bottom notes... this is done by giving the finger that plays the top note a little more weight and strength while playing the notes under it softer.
Well, if a teacher knows this, he/she MUST be an excuisite teacher! (yeah, its sarcasm)
Find out what the piano teachers credentials are. Go to their organized recitals. Ask them to play for you. It is your money you will be spending. You have every right to a professional interview. Then find at least a few other piano teachers and do the same. With a couple comparisons you should be able to see a difference in quality. Then you need to decide how much you are willing to pay.