I tow my S13 often on an open 18' steel trailer with my V6 4Runner just fine. I got a Hayden 677 trans cooler (barbed, roughly 3/8" - came with everything you need besides that I'd recommend you fabbing a bracket to mount it).
I went with a Hidden Hitch receiver and an Ultra-Fab weight distr. hitch. If you're not going to tow much, it'll be fine with a normal hitch though.
Air up the trailer tires to their max (usually 50-51 psi), check the bearings and grease them before you set out. For an occasional tow, the Tekonsha POD brake controller is cheap and works ok (turn gain down when in parking lots and backing up). You can get the Tekonsha harness and plug it right in. I'd recommend a P3 if you're going to tow with any regularity.
It's hilly just north of me where I usually tow, so I just leave in 4th and tow about 65-75 mph. Not a big deal.
Gas mileage does suck, you'll average about 11-14 mpg in my experience, so take that into account. But gas is cheap now, so that's not so bad.
I say go for it. It's not stressful at all if you just put it in 4th and cruise at 65 mph in the right lane. The only bad part is when yahoos cut you off for no damn reason or almost slam into your trailer at 25+ mph over the limit because they're txting or whatever people do these days besides driving.
