Those elbows thread into the valve, then there is a jam nut that locks it into position. First, you need to loosen the jam nut, so you can rotate the fitting.
Unfortunately, if the elbow does hit other fittings, you do need to pretty much remove the fittings in the way.
For the leak, there is a washer and a O-ring under the jam nut. That's the O-ring you want to replace because it's leaking.
Or, you can just try to tighten the jam nut a little bit and see if it stops leaking. Sometimes it's all it takes.