The best airport to use is Baltimore-Washington International, which is about 30 minutes away from Timonium, depending on traffic. A taxi or rental car would be best, and Timonium and the area of the fairgrounds is near a main highway and very easy to find.
I would suggest staying at the hotel where the seminar is being held (I think it is a Hilton), which is about 1/2 mile from the fairgrounds where the show is held. There is also a Red Roof Inn a couple of doors down from the Hilton.
The show runs from 9am to 5pm on Saturday, and 9 am to 3pm on Sunday.
Here is a link to the sponsor's web site:
http://www.baltimoreshow.com/