Before you start, know that even after you remove the clamps, the hoses will probably be stuck to the heater core pipes.
It'll help to get the air duct and fuel line guard out of the way.
Use a long screwdriver to remove the hose clamps. If they are at a bad angle, you can use that screwdriver to lift them to an angle that's easier to reach (provided you have sufficient strength in your wrist).
After you remove the clamps, use the screwdriver to
stab and scrape at the ends of the old hoses, tearing them. Eventually you'll damage them enough to make them easier to pull them off the pipes.
If you have spring clamps instead of the screw-tight clamps (pictured), you'll have to get creative on removing them. You could try prying them off with the screwdriver. Now is a good time to replace them with the screw type as they're much easier to deal with.
While you've got every thing apart, take a second to wire up a path to ground to protect the heater core from corrosion due to coolant developing a charge. You can use a multimeter to find a low resistance surface to which to fasten the other end of the wire.
Rub some dielectric grease on the pipes to make it easier to slide the new hoses on.
