If you never made any after-tax contributions to your pension while you were working, then you can short-cut the interview by entering the box 1 amount in box 2a and then in the interview, tell TurboTax that the tax this year is the same as last year and box 2a or whatever you need to do.
If, however, you did make after-tax contributions to your pension, then, yes, you will have to go through the Simplified Method to determine how much of your distribution is the "return of basis" (the after-tax contributions) which is not taxable.
The best thing would be that you had worked for the same company with the same pension plan all these years, and you could call the pension administrator for the answers to all those questions.