Valuing property held in 401k

[Skip Reath]

Have a question regarding valuing property held in my 401k plan.   In speaking to my 3rd party administrator regarding converting some of my 401k to the Roth election and paying the taxes they said I would need to get appraisals on all the property held in my 401k.  According to them this is the only acceptable way to get accurate values for determining plan asset value.  Is it possible to use the taxing authority assessment along with a licensed broker’s opinion as to the values.  Would like to avoid having to pay for multiple appraisals. Has anyone had experience doing this?  Thoughts??