the original original was circa '72. but actually what you'll remember was built/renovated in 'o7 for ~$8mm (see below). capacity of the stadium will remain a shade over 50k. i believe john currie said the new building will add about 1000 seats but they may take down some temps on the south side. the new building will be closer to the field with the seats at a much steeper slope making for better sight lines.
it is connected to the west stadium stands, but the east side connection is the next phase that will require work on the existing stands. they're not completing it now due to permitting issues associated with renovating the east side where the students currently sit. this rendering is from the north looking at the northwest corner of the stadium.