Prepaid funeral expenses 15 years ago, with 3.6% interest, should estate get some money back?

My wife and I are executors of the estate of a recently deceased neighbor with no family. She had very little. She had prepaid for her funeral, which of course was very small during the current pandemic. The director was vague about things costing a lot more now, and suggested that he made little to nothing. This is not something I deal with on a regular basis…

Should I simply ask for a full accounting – how much was paid 15 years ago, how much there was at the time of death with interest, and then an itemized list of expenses? For instance, there was money for an organist, but there was no organist. But he said digging the grave was charged $300 15 years ago but actually cost him over $500. She prepaid extra for a Saturday service, but we had a Monday service. I don’t want to be counting pennies, just curious what the etiquette is on this sort of thing. There are a lot of expenses and little estate to cover it all…

What is the "normal" way this happens? When the deceased has prepaid with an interest bearing arrangement, should the estate just assume that its covered and that there is no extra that may come back to them?