[Also, if I get new travlers for main and jib do I need to replace tracks also?]
Only if the new travelers won't fit the old track. I believe a Harken traveler would fit that track.

[How about down haul? is this an option I should install?]
Yeah, there was a downhaul on the boat and you will need it once you start understanding which sail shape to use in different wind speeds. See the photo I sent labled "Sol 18_1.jpg". You can't tell much about it but there is a downhaul there.

You will usually not want to drill holes in a hull any more than you would want to drill holes into your head. Since most of us have a surplus of holes there already, go to Plan "B". There should be a hole in each end cap for routing the bungee. Run the bungee through the forward beam. In that same photo you can see that the bungee is routed from the dogbone through the end cap on the forward crossbeam, through the beam, and out through the cap on the other side to the dogbone. You will need a plastic insert of some sort to place in the end caps so that the bungee doesn't chafe on the hole edges. You will have to drill the rivets out of the end caps in order to remove them.

In the same photo on the port side beam cap you can see the dogbone. It looks like a couple of links of chain just above the end cap. The tension on the bungee has to be only enough to keep the bones in place when not in use which should be enough stretch to make the trip out to the hook on your harness.