I planned my wedding in about seven months. I'd have to say that the majority of the stress was tying up loose ends very close to the big day. If you're planning to get married next summer, could you take time over Christmas break to finalize your location? I think once you do that, much of your current stress will be eliminated. Depending on where you live and how flexible you are (time constraints, etc.), finding a summer wedding date shouldn't be as much of a problem as you think! For instance, more venues are available in May than in June or July. Also, the
time of the wedding is a big factor. We had our wedding at 10 am, followed by a very nice brunch reception. One of my friends had an early evening wedding, followed by a decadent dessert reception. Having the wedding and reception in two different locations may make it easier as well because you'll be reserving the venues for shorter blocks of time. For example, we were married in my undergraduate chapel, and they rent the chapel in exactly two hour time blocks to allow for maximum utilization.
Do have someone that you trust to help you with the planning? For my friends that have married while in medical school, they definitely have relied on outside help (mom, maid/matron of honor, wedding planner) to take care of many of the details. Then on periodic breaks (Christmas, spring break, long weekends) they spent time in the wedding locale making arrangements.
Overall, I think it can definitely be done with minimized stress to you. But I think you have to be willing to let others help you and make
some decisions for you given your med school schedule.
Good Luck!