Is it possible to have one of your experts review my return even though I have already filed my taxes for 2017?

Yes.  If they find any errors, you can file an amendment.

If you’re using the Deluxe, Premier, or Self-Employed TurboTax Online product, you can add Expert Services. This will give you live tax expert help whenever you need it, as with the TurboTax Live product. It also gives you the opportunity to have a final review of your return when you’re ready to file.

You can now add Expert Services, follow these steps:

1. Make sure you’re signed in to your current TurboTax product.
2. Select Help at the top, and then Contact us.
3. Now enter "Add Expert Services" in the Ask a question box, and select Continue.
4. Select Speak with a live CPA or EA.
5. Click Get Expert Services.
6. Select Talk to an expert.
7. Now that you have Expert Services, you'll be able to connect to a tax expert.