Peach Tree Issues

Let’s address the Peach Leaf Curl first: once it shows up in the spring, there is nothing you can do short of removing and properly (do not compost) disposing of all affected plant parts. Before you plant, it is a good idea to choose a peach variety that is Peach Leaf Curl Resistant. If you don’t have that luxury, the tree needs to be treated when it is dormant. Here is an excellent link that might be helpful:
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7426.html
Regarding the aphids: It sound like you already have some knowledge of the relationship between the aphids and the ants. Getting rid of the ants is helpful as they protect the aphids from natural predators. Getting rid of the aphids may prove a little more difficult. This is a good aphid link:
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7404.html
This a little more advanced link regarding peaches in general:
http://www.ipm.ucdavis.edu/PMG/selectnewpest.peach.html