I have no good advice for you here... I've never been able to buy any vehicle from a big dealership.
I go with checkbook or cash in hand to pay for it right there.
Never had a car payment, never want to.
They never like that, they always want to finance ...no matter what we've got the best financing... blah, blah... what they don't tell you is every 0.1% they jack your rate up, the more money goes into their pocket for the term.
Who wants to pay $24k for a $15k vehicle? Not me.
Give them a firm, but low offer. Tell them you have a sizable down payment or whatever you have. Unless they have 100 other people willing to pay their price that can get financing, they'll negotiate. If they won't budge, show them the NADA or Kelley Blue Book value you printed online that shows the truck is worth $XX,XXX.XX which is far less than their asking price. If they still won't budge, move on to the next place. I wouldn't do business with a place that played hard ball like that... what will they do when you bring it in for warranty work... tell you to go fly a kite?
Also, if you can visit your bank, credit union, etc and have a pre-approval for a certain amount in hand, they know exactly how much they'll make for a minimal amount of work.
The auto industry is still swirling the bowl & no matter how fancy their suit or how polished their desk is, they're hurting for money.