I cooked my live rock for nearly nine months... that killed the HA, but still left a bunch of dead algae that is now decomposing in my new tank.
If you only have a weekend, I would cut the HA down and suck it out, then scrub each rock with a very stiff nail brush, rinsing it in salt water, then leaving it in the dark for the rest of the weekend or even a week or two if you can. As long as you're removing most of the algae you're cutting/scrubbing off, then you shouldn't have a problem with nutrient spikes from die off, and your beneficial bacteria will be fine as long as you keep the rock in aerated, heated saltwater. If you do that, then raise your Magnesium levels really high when you set your tank up again (I've heard as high as 1500-1600 ppm... I haven't actually tried this though), then the HA should have a hard time recovering. I know my tank looked way better even after just scrubbing the rock and putting it back in the tank, and the HA grew a lot slower afterwards. I've killed HA with boiling water too... works good, but you will kill everything else on the rock, and the dead HA stays attached to the rock. Maybe good for getting rid of small areas that are completely covered in HA.
Anyway, hope this helps. I'd say go for it. You can't do too much damage unless you boil all your live rock.