How much is Amur leopard skin worth

Hello everybody,
a warm hello to everyone. Thank you very much to everyone who lets me share their collector's knowledge.
I have a full set of the Pokemon Basic Edition (102/102) - first edition including some double holos like Charizard, Simsala, etc.

The degree of preservation somewhere between 6 and 9, I would say, depending on the map - on average 7 to 8 so near mint. As a result, an "estimate" is very difficult, I realize that much. The price of the collection is determined in particular by the "Most Wanted" cards

How would you approach an orderly sale of the collection?
Would you have GSG graded in Germany, for example, to give a potential buyer security?
Are there cards other than the holos that should be graded? Pikatchu or something like that ..
Where does it make sense to sell these cards?
If you feel like it, you can estimate the value

Thank you for your expert advice!