If you are named a primary beneficiary on the IRA account - you simply may contact the administrator of that IRS and request a distribution according to your grandmother direction.
You will be asked to provide a death certificate.
There are several options...
You may request a full distribution OR
you may open so-called inherited IRA account and start periodic distribution over the lifetime OR
you may take full distribution within 5-year period.
Please be aware that distribution will be reported as your taxable income - but it will NOT be subject of penalty regardless of your age.
You will receive a reporting form 1099R that will be used with your tax return preparation.
As a resident of California - the distribution will be taxed on the state level.
Medallion signature guarantees are required to transfer or sell securities in physical certificate form. Most likely - securities are held in IRA account are NOT in the form of a physical certificate - and that form is not required.
I suggest to contact the administrator of that IRA and verify if that form is still required and inform them that you were asked about the value of the account.
Because the physical certificates are rare nowadays - some banks may no longer provide this service. Some that do provide - may have different requirements for documentation necessary to proceed. Thus the law doesn't require to have the account value - but if the bank requires that - you may simply use estimated value.