Chris,
First step to see what your pathfinder can tow is to look on the certification sticker on your driver's side door jamb. It will indicate the GVW, GAW, and possibly, the maximum weight of "all cargo and passengers should not exceed..". What you need to determine is the payload weight capacity of the vehicle. Just a fast search online showed the Pathfinder to have a payload capacity of 1170-1550 lbs.
From the payload capacity, an owner works backwards subtracting the tongue weight of the trailer, the weight of the weight distributing hitch, the weight of any cargo, and the weight of the passengers. If the total falls under the payload capacity, you're within the vehicle's rated towing specs. Most folks find that they run out of payload capacity before they reach the maximum towable weight rating.
You should also look at how Toyota equips the Pathfinder for any optional "Towing Package" (if you don't have it). Things like tranny coolers and oil coolers, better suspension, etc. They can all make a difference as to how the vehicle tows or if it has problems without those accessories.
I have no wisdom for you about new trailers. Mine is old as the hills but has been restored. Good luck with whatever you buy and happy trails to you and the family.
