Unfortunately, Form 3115 is out of scope for TurboTax. My best advice is to see a professional preparer if you don't feel you can fill out the form without help.
Below are the IRS links related to the change in accounting method. TurboTax does not have that form.
Maybe these will help
Form 3115, Application for Change in Accounting Method
Instructions for Form 3115 (03/2012)
Form 3115,
@cbusa wrote:
I believe I need to file form 3115? Is there a demo properly completed form for this scenario to see as an example?
No, there is no "demo".
Although Form 3115 is included in TurboTax, it must be completed entirely in Forms Mode (which requires a desktop (installed) version of TurboTax.
Regardless, a demo would not serve any purpose whatsoever for your purpose. The section specific to the situation that you would need to complete (Part IV - the Section 481a adjustment) is rather simple, but you still have to include a statement that precisely details the adjustment.
Further, you have to complete the first two sections which contain rather arcane and convoluted questions, et al.
Further still, you can e-file your return with a 3115, but you also have to print and mail an additional copy to the IRS.
Bottom line is you need a tax professional for this scenario.