[ac10]

1. How far should I go? Keep in mind I haven't done laps in a couple years.

It seems like if you are just getting into swimming you should try to go for time rather than distance. Just keep your heart rate up for 30 minutes to an hour. Doesn't really matter how far you go.

2. Should I try to change strokes? (Currently I'm only semi-proficient in the crawl, and can't do the others)

Once you get comfortable doing a good ammount of crawl stroke you should learn to do back stroke. It will work a lot of different muscles. Don't do breaststroke nobody swims it fast enough to be a good workout. As far as I can tell people who aren't in shape swim breast because it's way easier than the other strokes. If you want an awesome workout you can try butterfly. However fly won't be easy until you are a fairly advanced swimmer.

3. Would going hard and taking breaks be the best plan (kind of interval training?), or should I just try to do a steady rate?

I would suggest for the first few work outs you swim until you need a break than rest for a while than swim more. Swimming is very demanding and it's hard to go very far unless you are conditioned for it. Once you get in better shape and can go for a while than it is better to do interval training. An example of this would be swimming a 200 warm up than rest. Then go 10*100 crawl on a set ammount of time (this can be 1min. 20 sec-3 min depending on your 100 time). Ideally you would be getting 10-25 sec between each 100. Then cool down. As you get better/faster you can add more sets in between the warm up and cool down.

4. If I do this in the morning, would I be able to lift upper body in the evening?

Yep