You did not kill the roots by doing this heavy pruning so you have a good chance that the shrub will produce new stems from the crown in the Spring. If this variety blooms from new wood then you will get flowers in 2009. If it blooms from old wood then it will skip flowering in 2009 (but some varieties may surprise you with a limited amount of blooms).

Yes, any plant that is transplanted will be stressed. On the other hand, it is getting stressed annually during the summer due to too much sun. If transplanting corrects that annual summer stress, I would consider moving it now while it is dormant. Transplanting during this time is less stressful. Try to move as much of the rootball as is practical. Get help moving the heavy root ball if you need it. Mulch afterwards and keep the soil moist (not wet). Insert a finger to a depth of 4" and water when the soil feels dry or almost dry.

Here is a link that might be useful: Transplanting Hydrangeas

I'm chiming in late, so I hope you see this. First, congratulations on your new house. Second, if you bought the house in autumn, and one hydrangea's flowers were starting to brown, that's exactly what it should have been doing in autumn. My guess is that the brownish one is the healthier of the 2. It probably flowered on time in the summer while the one in shade flowered late. That's why the one in shade was still blue in fall.

You're probably not going to love my advice because I can tell you're itching to get out there and fix that yard, but I'm going to suggest that you wait. See what your plants do this year. Learn what the sun does in your yard throughout the season and adjust your plan accordingly. You may find that although overgrown, some plants are in exactly the rght spots. You can transplant the ones that did not do well in fall or next spring. Plants can do fine with a transplant. Plants will not do so well with several transplants. So learn what you've got before digging.

Good luck.