Unless your taxes are extremely simple, you may need outside advice. We use one of the two main tax software packages.
For security reasons, we do not use online tax software, and we do want our tax information to exist in any tax preparer's computer systems. Further, we do not store our returns on our own computer.
To compare various Roth conversion scenarios, I created many pro-forma tax returns for future years, (through age 71) to determine the tax and budget consequences of various plans. There are Internet calculators available to assist with this process. Many financial planners offer to help with this decision. The quality of the advice varies greatly.