First, let me congratulate you on your first batch!
I can understand your confusion due to the plethora of opinions and techniques concerning carbonation. If you just racked to the keg, hooked up to CO2 at 30 psi, and chilled the keg, your beer will not be fully carbonated by now. But if you tap the keg and try to pull a pint, beer will probably come out really fast, and you'll probably get a glass of foam.
30 PSI is too high of a serving pressure for most homebrew setups. The ID of your beer line provides resistance. You must have a sufficient length of beer serving line to compensate for the amount of pressure in your keg. But don't worry! You haven't created any problems yet - there's nothing wrong with having 30 PSI on your keg for a day. It takes a while for the CO2 to dissolve in the beer and it shouldn't become overcarbonated in one day...but it probably would in a week. In order for a beer to become carbonated to a certain volume of CO2, the beer must be
exposed to a certain
pressure for a given amount of
time.
Time - The simplest process with the least chance for error is to set your regulator to your serving pressure, hook up the gas line, and leave the keg in your kegerator for a couple or 3 weeks. There's nothing wrong with pulling a pint every now and then - it just won't be fully carbonated at first.
Pressure - Another method would be to set your pressure high, like 30 psi, and leave it for a couple of days, then back the pressure down to your serving pressure. Increasing the initial pressure will shorten the amount of time necessary for the beer to carbonate.
Exposure - You can use a carbonation stone, which creates tiny bubbles of CO2, effectively providing a greater area of exposure.
Exposure and pressure - You can use the crank and shake method, where you crank up the pressure to 30 psi, shake or roll the keg for a while, then bleed the pressure out of the headspace and back your regulator down to serving pressure. This will get your beer carbonated in the shortest amount of time, but you run the risk of overcarbonating your beer.
Personally, I hook up a keg at serving pressure and shake it for a couple of minutes - until I can hear that the gas flow through the regulator is slowing down significantly. Then I put the keg in the kegerator and leave it. If I think about it the next day, I'll shake the keg again, because it will readily absorb a good bit more CO2 once it cools down. Then I let it sit there a couple of weeks before I touch it. I do it this way for two main reasons - there is no risk of over-carbonation that I'm aware of. And most importantly -
your beer will taste better after it's aged for a while in the kegerator. For example, my wife and I sampled my cream ale after 2 weeks in the keg. We both said it was 'pretty good' but we agreed to give it more time. The next time we tried it was after 1.5 months in the keg, and we gave each other the 'this is a really good beer' look. The keg was gone within 2 weeks, but without a doubt, the last pint was the best!
I digress. You said your temp is in the high 30's. I'll assume you're at 38 degrees, and you want to carbonate your Hefe to 3 volumes of CO2. (This might be a little low for this style, but I think it will be fine.) For your situation, I recommend that you give your keg a few shakes at 30 psi. Disconnect the gas line. Back your regulator down to about 16 PSI. [This assumes that you have sufficient length of beer line to provide a proper pressure drop...I think you need about 2 feet per PSI, or 8 feet in your case.] To get an accurate reading, you'll probably have to toggle the pressure relief valve on the regulator. Bleed the pressure out of the headspace of the keg and hook up your gas line. Sample your beer. Drink it when it seems carbonated and starts to taste good. (I would tell you to try to pace yourself - you'll be surprised at how good it tastes after a couple of months.....but it's your first batch. It won't last that long.)
Sorry for the long winded reply, but to answer the question in your post, no, it's not that simple, but yes, you will be drinking your first homebrew tonight!
Cheers!