They said to you: they don't like to have Toyotas sitting in their lot, because then it gets sent off to auctions or priced below book value.
So, did you guys, look at what the "blue book value" is, for a used Toyota, for that same model???
If not, do that.
Google search it online.
THEN, compare the Blue Book value, with the price that that Dealer is offering you.
Then, think about the mileage that is on it.
You said it is really high....
Then, aside from that, you said it is a well kept vehicle. With only minor scratches/small dents that are usual with a vehicle/family van, that is of a 2004 year.
We have a Sienna. And ours is newer. We have minor scratches/dents on it too. From usual usage.
Siennas are very good.
We have never had problems with it. We also maintain it and take it in for regular servicing. Which should be done for any vehicle anyway.
As an aside: I would ask them if the van comes with TWO car keys/remotes. Not just one. Every Sienna, has 2 keys/remotes. Ours was bought brand new, and it came with 2 key sets.
Leather interior, is easy.
I had a car with leather interior.
Its perfectly fine and nice.