300 Level side seating is split up into lower and upper portions. Rows A-E are on the lower portion, while the rest of the rows are up a staircase. If you can afford it, stick with seats in the lower rows. This will leave you with fewer stairs, quick access to the concourse and much, much better views of the action.
Sections 324-329 contain the most rows of upper level sections, and the top rows (above N) will have you wishing you sat much lower.