Hello :-)

At lowes, I've picked up 2 tardiva hydrangea tree forms. They were marked half off because them seem to be pretty neglected. This is my first year gardening, but I've learned hydrangeas are pretty tough, so figured they would bounce back! Problem is, the branches are really bent over to one side, and alot of branches seem to be dead. It does have flowers on it, some are brown, leaves are mostly only of the top, and the bottom looks pretty sparse. I would like to plant it soon, and was wondering if its okay to prune back the dead branches before planting? Or should I wait until its dormant in the ground and then trim, or just leave it be until spring? Also, when pruning this plant in general, how far back should it be trimmed from the main stem?

Thank u greatly for any help and info in advance ^_^