found out what my truck is rated for got questions now

Forest River, just like every other manufacturer, makes good trailers and bad trailers. If this trailer was one of the bad ones that came off the line, it would be blatantly obvious in 2017. Still I would thoroughly inspect it for current or potential problems. If you aren't capable of performing the inspection then hire someone to do it for you. I wouldn't trust the dealer's inspection.

It's certainly possible to tow with your current truck. You may want to first scale the truck, loaded as you would for a trip and a full tank, to determine what amount of payload you have left for a trailer. Once you find out how much payload you have available, then you can figure out what's the max tongue weight you can carry.

The tongue weight is typically 13 percent of the total weight of the trailer. So if you were to max this trailer out at 8,400 lbs then you would need at least 1,092 in available payload to stay within capacity. 1,100 lbs is more realistic.

Neither the dry weight or the GVWR of the trailer matters. What matters is the current weight of the trailer when you're towing it. Just because your trailer has a high GVWR doesn't mean you have to load it up to that weight. For example, I tow a trailer that has a GVWR of 9,990 lbs. My scaled trip weights are no where near that nor do I pack enough stuff to get there.

Ask the dealer to give you the current trailer and tongue weight so that you'll have a good starting point on your calculations.