1) is it normal to feel so shattered and slightly ill after rowing, or is it likely my eating throughout the day (and last night's pig out - turned 20! Not much drinking mind you, as the night out in town was done on Saturday) along with jumping into it a bit too hard are the reason I feel this way?
Rowing is a humbling Experience. It is one of those things that if you put all out effort into it, you will be absolutely smashed. I would say you might have gone too hard as a first workout. I do know on the Concept 2 website they advise starting at a shorter distance and working your way up so you can figure out your comfort zone for Damper Setting, pace, etc. In my experience, I am only ever wrecked from a rower if I am going as hard as I can go. For example: My warmup every day is a minimum of a 2km Row. I tend to go with upper medium intensity in order to finish in 6:40-6:50. With this pace, I am completely fine to get off and walk around.
On days that I am going as hard as I physically can, I will hit in the mid 6:20 Range. During these days I peel myself off of the rower and need to sit down for a minute or two to catch my breathe.
2) I began to actually get a feeling of discomfort/tightness/bordering on minor pain in the front of my shoulders when rowing. Any ideas what caused this?
Are you getting warmed up before rowing? For you it might be good to do some mobility exercises to loosen everything up pre-row.
3) Likewise, knees were pretty uncomfortable at certain times too. When going back into the catch, should I let my heels raise up off the foot-rest, or should I restrict my range of motion so that my feet stay perfectly flat? I'm wondering whether going so far forward that I went up onto the balls of my feet and then quickly getting back onto my heels and slamming back may have been bad on the knees.
Part of this can be connected with my answer in #2. As for the Heel Issue, When you are transitioning from the Recovery to the Catch and Drive, you should be planting the balls of your feet (Your heels will pop up a little bit). You should not be slamming the heels back, when you are in the Drive phase, your body will extend and should inevitably make your heels drop back to a planted state.
If my explanation is awkward to read give this a look over:
4) a more difficult question, but one worth asking - what kind of rowing workouts should I be doing? My main goal these days it to cut bodyfat, but at the same time I'm using the rower in an effort to get fit. As mentioned earlier, I'm sedentary, and as result am woefully unfit. Even if the place I lived in wasn't a total dive that's depressing to go running around, the last time I tried it I was gassed within a few minutes of running, so rowing, which I find really fun, just seems to be the most practical thing for me to use for fitness, since I know I'll actually stick to it. Question is, what should I be doing to get my fitness up? 2k ? 5k ? A different pre-set workout, or something entirely different?
I would suggest a little bit of everything. By this I mean mix up your workouts into Intervals, Medium distance and Long distance. Concept 2 has daily workouts which fall under the Short/Medium/Long range that you can pick and choose. Some examples I will give you of ones that I do very frequently are:
2km Row for time (Medium), 5km Row for Time (Medium/Long), 10km Row for time (Long), 10 Intervals of 500m Sprints with 1:00 Rest, Intervals of 1000m/2:00 Rest. There are a lot of workouts you can do. If rowing is going to be your go to method of fitness, I would suggest looking at the Concept2 daily workouts found here: http://www.concept2.com/indoor-rowers/training/wod
Hope this helps!