I think you maybe understimating the total weight of your loaded trailer. Most trailers are 2 horse and weigh closer to 2,000 lbs. The fact that it has trailer brakes is another hint it is heavier. An average horse weighs over 1,000 lbs too. Combined with water, and tack you are going to be closer to 3,500 lbs.
Just because there is a hitch available doesn’t mean the vehicle is rated at 3,500 lbs towing capacity. If you still have the owner’s manual it should give the towing capacity. If you stick to short trips with no interstate highways you might get away with it. Safe? No, you are overcapcity. Will it damage the Montana? Yes, the transmission will take a beating and will be prone to failure. Check out the cost of replacing the transmission before you proceed.
Best option is selling or trading in the Montana for a more capable tow vehicle. I did just that; sold a '98 Volvo wagon with 3,500 lb capacity for a '01 Toyota Sequoia with 6,500 lb capacity to tow my 2 horse trailer.