I, too, was wondering about the year and drivetrain (engine & transmission) of your 4Runner. A 3000# rating could be somewhat marginal for mountain towing, depending on your performance expectations. A Scamp 16 typically weighs 2500-2600 pounds with the usual options and packed for travel.
I'd discuss the plan with a trusted mechanic who has some knowledge of your vehicle and its condition. If it's an automatic, I'd discuss whether it would benefit from an auxiliary transmission cooler. You might also check out the towing section of a 4Runners owner's forum and perhaps even pose the question there. Tow ratings rarely tell the whole story, and ideally you want to hear from someone who has towed with the same vehicle and drivetrain.
Scamp 16s are great little trailers. If you anticipate using the bathroom a lot, the front bath is more usable. If it's only for occasional use, the side bath allows for more galley space. The main dinette bed is pretty small for two, at 45"x76" in all 16' standard layouts. The deluxe (wood interior) models have a wider 54" bed, but they're a bit heavier, more expensive, and harder to find used. If you're traveling solo, the front sofa makes a nice single bed, leaving the dinette free for day use.
Lots to consider, but the best way to decide is to tour some actual trailers. A rally
is one way- most can accommodate a day visit, and owners are usually happy to show off their trailers. Some even have a scheduled open house time. Another is to work with Scamp's sales department. They have a referral program to set you up with a nearby owner for a demo.
Happy egg hunting!