I have a multigraft peach tree that is about 7 feet tall and it has some marble sized peaches on it. I just purchased this tree and it is very vertical in its growth habit. I was wondering if I should prune it now or wait until summer or winter. I'm willing to sacrifice this years fruit if necessary. I've read that I should prune it to have an open center which means I will have to prune off many of its branches.

When I planted the tree last week, it was severely potbound so I had to scratch the root area and destroyed some of the peripheral roots in the process. I also pruned off a few small poorly positioned branches and removed 70% of the fruit it was holding.

I would greatly appreciate any advice on when I should prune. Are there any good sites with pics on how to prune? I found many sites but
Most talk about pruning whips or trees that that were already partially trained with an open center. I would say I have a third year tree that was neglected in pruning. Thanks in advance!
Simon