It's a hard lesson to learn, but your banker doesn't provide tax advice. (Your broker and your insurance agent don't either.) That said, it's a common issue for beneficiaries to miss the required minimum distributions, or RMDs, out of a 401(k) or traditional IRA, especially if the deceased didn't take RMDs in the year he died but was required to do so.
You may have to pay the piper in terms of paying an additional tax on the excess accumulation, which is the difference between the amount that was required to be distributed and the amount that was actually distributed. The Internal Revenue Service calls it an "excess accumulation" because you haven't taken the RMDs, and by not doing so, you've allowed the account to accumulate. The additional tax is 50 percent of the excess accumulation, which is the difference between the amount that was required to be distributed and the amount that was actually distributed, so it's a very stiff penalty.
The IRS can waive part or all of this additional tax if you can show that any shortfall in the amount of distributions was due to reasonable error, and you are taking reasonable steps to remedy the shortfall. The instructions for IRS Form 5329, "Additional Taxes on Qualified Plans (Including IRAs) and Other Tax-Favored Accounts," explain the steps you need to take to request this waiver. The IRS reviews the information you provide and decides whether or not to grant your request for a waiver.
You want to get current on the RMDs. Beyond that, you would want to manage any additional distributions out of the account to manage the tax impact of those distributions. Moving your income levels into a higher marginal federal income tax bracket will increase your total interest expense. While there are RMD calculators available online, because of the excess accumulations in the account, I suggest working with a tax professional to request the waiver, determine the RMDs and decide on a distribution strategy for the balance.