I don't have any experience with disc brakes (at least not on a trailer), but I just recently finished installing a complete new drum brake setup on my trailer. My trailer originally came with brakes, but there wasn't a usable component left on them; so I got new everything. For me, it was a big improvement, but bear in mine that my rig is probably tipping the scales a little north of 6000 lbs. Also, I'm taking it on an 8 hour tow into the Arkansas mountains for July 4th. Therefore, I'd say I have a greater need for trailer brakes than you do.
First thing you need to do is to verify that you will be able to fit either type of brakes to your existing front axle. For drum brakes, there needs to be a square shaped flange with 4 holes (1 at each corner). This flange should be located between the spindle (stub axle) & the main part of the axle on each side. It's where the backing plate bolts on. For disc brakes, I'd presume that you'd need some sort of caliper mounting bracket attached to the axle, but I can't say for sure. If there's nothing on your axle to which the brakes can be mounted, you'll need a new axle designed to accept brakes. If your axle will accept drum brakes, I'm not sure if there exists any sort of conversion kit that would allow you to fit disc brakes without changing your axle. If not, you'd need a new axle to go with discs as opposed to drums.
My setup cost me a total of about $250 with tax from Husky Trailer Parts on the South Loop @ Telephone. That's $100 for a new coupling with master cylider; $30 for a kit containing all the necessary hard lines (already flared, with fittings, & cut to length), the flex line, & T-fitting; $50 each for 2 complete drum brakes. Each one had the backing plate with the wheel cylinders, shoes, adjusters, & springs already mounted to it. All I had to do was bolt them to the axle. I also needed an additional 2' of line & a double female adapter because the line running from the M/C to the axle wasn't quite long enough, & I needed new bolts to mount the brakes to the axle. I'd presume that a disc setup would cost a good bit more, & I doubt you'd need the additional stopping power. As for maintenance, longevity, etc, I'll have to report back later.