Beginner Gardening: MUST transplant lilac now instead of spring.., 0 by LateToBloom

LateToBloom wrote:
Thank you one and all for the advice.
themoonhowl : You advised me to trim it back as far as possible, and I'm willing to sacrifice all of next year's blooms to keep it alive, but I'm not sure how much is "as much as possible", all I've ever done is cut off the blooms when they are spent each year, and clipped off the new branches at the trunk to keep it from getting in the way of the door to the porch. Do you mean I should cut the height of it down too, and if so, how much?
RachelLF: I don't think it is the one called "old fashioned one", it is a very deep dark purple and highly fragrant too. My husband bought it for me the year we met, and I would hate to lose it no matter what kind it is.
Joan: I'm posting a picture so you can see the size of it, and I would surely appreciate any comments on how wide and deep to dig to avoid disturbing the root system more than necessary. The top of the door is 6' 8", and the lilac is 2½ feet taller, but as you can see it isn't very full.