Mr Mag, you might have a word ot two here.
Handguns are weird, especially in MI. When my father died, legal title and registration of them passed on to my mother. To give them to me, the local PD generated blank purchase permits for each one. She would fill out her part as seller, with me as buyer. Then I took them back to the PD, they stamped everything, and they then had new paper that said I was the owner.
It was all free back then, but since there were about a dozen handguns involved, they only did three a week because otherwise it was too much effort for them. They notarized each form for free, but would probably charge $20 apiece now because they are desperate for money. They were actually quite cooperative for being bureaucrats.
This may change soon, because Michigan is starting to realize that state, county, and cities spend millions of dollars a year for a 1930's registration that has never solved a single crime. The federal NICS system is free for them, and even though it's still basically useless, it would save them real money every year.
A bill in the state senate has already passed that would treat handgun sales in Michigan the same as long guns. The feds would be involved via NICS for every sale that goes through a FFL holder, while sales between individuals would go on as before, but this time including handguns.
I don't think this will be seen until after the November election, because the governor doesn't want to make waves.
One word of warning
Widows are especially vulnerable to "friends" of the late husband who stop buy and offer a disgustingly low-ball price for the whole collection, out of their concern that she not be cheated by "unscrupulous" collectors who would offer her even less. If nothing else, if you have a conscience, make sure she has a realistic view of what the stuff is really worth.