Yellowing leaves are because of inadequate light. I suggest trying to wire to wire the branches in position so that light gets to the inside rather than cutting anything off. Sometime around August is a good time to repot it, IMHO. Then next spring think about cutting back and getting some back budding started. Stuff that is already yellow will most likely turn brown and brittle, but other greenish interior stuff will likely perk up.
On the other hand, if you bought this for styling practice, do it right away if you want. It is basically healthy, so there is no reason to rush into repotting. It likely can wait until next spring if you want.