I have switched to 134a on my old c4, and the vent temps were nearly the same as with r12, if done properly by the right a/c guys your car should cool just as well with 134a.
You don't need new hoses, but you need new o-rings, i think i used neoprene o-rings. If you want to do this yourself, it's actually quite easy but labor-intensive. At the very least you'll need a set of a/c gauges, a new accumulator, and a new orifice valve, PAG oil (8 oz if i remember correctly), a compressor to blow out your lines and condenser and evaporator, flare nut wrenches, and a vacuum pump. You can rent the tools that you'll need.
After everything is all tightened up again, you want to draw a vacuum and make sure it holds, then you can charge the system. It's quite satisfying to do this yourself. There are websites that walk you through the process. Good luck.