Narrow it down as to what exactly you want for your next car then do some research on here as to what they’re leasing for. “SUV or electric sedan” could be hundreds of different cars.
If you can buy your lease directly from MBFS then there is no need to involve the dealer, at all. You arrange financing on your own, send the money directly to MBFS using the instructions online, they send you the title. The dealer has nothing to do with this.
No reason to finance with MBFS unless they were to offer the best rate and terms. You just need to shop around, take a look at the below thread.