Can TurboTax help compare 2 years' tax returns for a fee?

Not sure what you are asking, but no.  Did you use Turbo Tax?

You can print them out and compare them yourself.  Although there are major form changes from 2017 to 2018.   

What are you concerned about?  Did you get less refund than last year?  For one thing, they reduced the withholding tables so you got more back in your paychecks each month.

if you used TT last year see if there is a tax history form.      if not, you'll have to buy the 2017 software and recreate the 2017 return.  TT is do-it-yourself software.