They usually run through the factory installed rigging tubes, but depending on the age of your boat, a previous owner could have replaced the hoses before and could possibly have rerouted them. Check the hull layout diagram for your boat provided by Grady and it will show the location of the rigging tubes.
It is normally not a tough DIY job. Sometimes the old ones pull out with no problem and sometimes not. If the old ones won't move, they may have been zip-tied or some such and it is OK to just clear the fluid out and leave them alone and install the new ones. If you are able to pull them, be sure to use them to pull the new ones in or at least pull a piece of paracord or similar through as you pull the old ones, so you don't have to snake something through.