I would wiat on aphid treatment until you see them in spring. Then I would start by just giving it a hard spray with the hose when the aphids get bad.

No fertilizer should be needed with new plants. Generally they come from the nursery well fertilized and adding fertilizer at this time of year when they are going into a rest period doesn’t make sense. See how they look next year and decide based on color and overall appearance whether they need anything. If they look healthy, don’t fertilize. Don’t expect a lot of new above ground growth for the first year or two because most plants grow more roots before putting on much top growth.

Make sure you water enough to keep the soil moist but not soggy until leaves drop, and mulch. If you have issues with winter munching by voles, deer, or rabbits, make a ring of wire mesh to protect them. Remember that rabbits will take advantage of the snow to eat plants far higher than they could normally reach.

I do not know where you are in New England, but crape myrtles are borderline hardy even in the warmest parts of New England, especially when fall planted. Give it protection from winds with a scree or use one of those shrub protectors, especially this first winter when the roots aren’t well developed.

I'm in Rhode Island - I have seen a few growing down here so thought I'd give it a try. The CM was planted in the spring so it's had some time to get used to my garden and its weather. I am going to mulch it and find a way to protect it. It is in full sun ALL day which they favor so hoping for the best. Thanks for all the good info.