All you need to do is keep it well watered :-) That's really all any newly planted plant requires. Hydrangea paniculata is fully winter hardy for your area so no winter protection required. No more fertilizing (new plants don't require any and it can impede establishment)!! Proper mulching may be all the additional nutrient supplementation necessary - landscape plantings seldom require much fertilizing. They get what they need from the soil. Any pruning you may need to do - and tree-form paniculatas often require some to the keep the canopy proportionally sized - should be done in early spring before the plant leafs out.

Should need little care except weekly water. You can prune any time, but too late (e.g. July) might delay flowering til Fall..

Ditto. I would put 2-4" of mulch and a stake to keep it in place if the area where you put it is windy or if it gets a lot of snow.

Congrats on the Limelight. That version in tree form is the favorite one of a local plant nursery. They had for sale this year and a couple years back and so forth.

I should have mentioned that I put down some mulch. I don't think I have quite 2" under it - but I ran out. I plan on buying more this weekend. I figured some was better than none until I could get more.

It sounds like you chose a good site for it since they like sun, and it's a great plant: long blooming, requires little care and is rock hardy, so I don't imagine it will take much after this first season. Mine (not Limelight - several different H. paniculata varies) are in beds that almost never get watered though they did the first couple of years when it was dry.