Not only leery, but, very, very concerned. While your Tacoma may have a 6K towing rating, that rating is for a frame mounted hitch tow, not a bed mounted 5th wheel hookup.
5th wheel trailers have a much higher "pin weight" than a bumper pull trailer, magnitudes greater. A 21' bumper pull trailer may have a tongue weight of 750 lbs, while the same 5th wheel length could have a pin weight of 1200 to 1700 lbs. depending on model, options and loading of the 5th wheel trailer. 5th wheel trailers carry their weight slung between the wheels and the hitch pin, while a bumper pull carries most of its weight balanced on the trailers wheels. Some bumper pulls can even be loaded so that there is negative weight on the tongue (heavier on the trailer's bumper end than on the tongue and these people have to take special precautions in loading to keep adequate weight on the tongue. I would be very concerned with the GVW limitations of your Tacoma.
I believe you will find that your Tacoma's load capability is around 1200 lbs and that has to cover passengers, options on your truck (like the 4x4; the front differential components count against the vehicle load) and any other cargo...kids, pets, "stuff" in the storage area and even the weight of the 5th wheel pin support (hitch). I think that you will find that you are overloading the frame and suspension on your Tacoma...that kind of loading can lead to suspension and frame damage and failure.
The pin loading on a 5th wheel is such that you will find that most 5ver owners tow with 3/4 ton and up, large block gassers and diesels, not V6 powered "compact pickups". Be very, very careful if you go that route. You are talking about an awful lot of weight. My 21' 210WBS comes in right at your towing max...the TT weighs 5975 for us, on the road, with a tongue weight in the neighborhood of 715-721 lbs. That would max out your Tacoma (if not overload it) and it is a "bumper pull". I pull with the vehicles in my signature; the Jeep is adequate and with the Hemi has an easy time of towing, while admittedly, my Ram 2500 with the High Output (800 ft lbs of torque) Cummins Turbo Diesel is over-kill (I have a farm and have other uses for the truck besides towing the FunFinder...).
If you go that route, find out what the "real life" pin weight is on the trailer and then calculate, very carefully, what the gross vehicle loading is on your Tacoma. I'm afraid that you will find that you will be overloading the rear axle (a 5th wheel hitch doesn't spread the load on the front and rear axles like a good weight distribution hitch does; all the pin weight goes on the rear) and most likely you'll be exceeding the total load capacity of the truck's engine, transmission, brakes and frame.
