Well, you should look up "3LB per light" in the "Grow room set up" and post this question for Tranable and he may be able to give you some good input on sealed rooms, but I will still try to give you some things on general principle. Generally each 1K light without air cooled can bring a 5x5 space up at least 10d in temps, when air cooled depending on the fans your using to pull or push the air threw the hood, you can drop that 10d down to about 5d or less. So right now if your room is approx 90sqf your ambient temps my go up approx 20D, or less depending on how good the fan system is getting that air out of your room, so based on that, if the room is 70d without lights, then theoretically you will be at about 90D with lights, and if you are going to use C02, which I would imagine you are if you are doing a sealed room, then you will be fine with higher temps in the 90's. If your not using C02 then you will need to get thoughs temps down into the 70's for the best results, though many people grow in the 80's.
You asked if you will need fresh air coming in for the plants I assume, well the plants produce O2 and no matter what your room will not be completely air tight unless your using NASA technology, LOL, so they will be fine without outside air being brought in by you.

"Will the heat from the lights still be too much for that size room w/o an a/c?" This all depends on your rooms ambient temps, for instance a room that I am setting up right now is about 50D right now because it has no heating in it and it is close to winter hear, if you have a sanario like this then you may be able to go without an AC for the next 6 months or so.
"I do not want to cut 2 6" holes out the wall and spend 3k for an a/c if I don't have to." I am not sure if your talking about cutting the holes for the AC unit, but there are AC units that actually recirculate the air with in the room that are not vented out side FYI.
Hope all this helps some.
Adieu