General questions for a tri-newbie...

1.  Total immersion is great.  The link in my sig also has the drills I found most usefull for learning to swim.  Side kicks and catch drills made all the difference in the world for my stroke.

2. I have never found a stationary bike to be close enough to a real bike to really correlate resistance to road feel.  I would personally work on longer easier ride focusing on keeping your cadence somewhat high.  Probably above 60.  Just keep your feet moving fairly quickly and don't pedal super slow on high resistance.  You could probably increase the resistance until you hit that point of not being comfortable, but I would stop there and not push it super hard.

3. Like was mentioned, I would keep walking longer.  The key to aerobic endurance and fat burning is long periods at low(ish) heart rates.  After that 30 min when your body's blood glucose levels start to fall, it will start to metabolize fat to replentish them.  The longer you walk, the more fat is metabolized.  If you push your HR a little higher, you are doing more work and burning those calories faster, so you start metabolizing fat sooner and at a higher rate.  This keeps speeding up with increasing effort until you hit about 90% of your LT.  Then you start burning more glycogen (a substance stored in your muscles) and less fat.  So anyway, you burn the most fat right under this point.  As long as you are working at a level that you feel like you could hold for hours, then you are staying aerobic and don't have to worry.  Just remember that pushing it past that point, to the relm where you can only sustain for a few minutes and it's not fun, is not getting you closer to your goal.  Since you won't be elevating your HR very much at all walking, you could incorperate elipical machine and pool running into your schedule, which allow you to up the intensity a touch without increasing the impact on your joints.

anyway.  Good job and good luck!

1) Cadence is how fast you spin the pedals.  So a cadence of 60 means you spin the pedals 60 times every minute.  That would mean one complete revolution every second.  If the bike doesn't tell you cadence, just count how many times your right foot passes a certain point (say the top of the stroke) over 10 seconds and multiply that number by 6.  Once you do it a few times, you'll get a feeling for what 60 rpm feels like and you won't have to count any more.  In my experience I have found that it is easier to raise HR by increasing cadence then by upping resistance.

2) LT refers to Lactate Threshold, which one would figure out through testing.  Maybe one of the coaches will chime in on this one, but since the LT test is very strenuous and geared towards people who are already strong runners, I would say your best course of action would be to esptimate your Zone 3.

In zone 1 and 2, you should feel comfortable.  Like you could keep running for a long time.  You can hold a conversation.  As talking becomes more difficult, you are reaching the top of zone 2.  Zone 2 stops and zone 3 begins at the point that conversation becomes hard enough that you don't want to do it.  You will also start to feel uncomfortable and like you are pushing the envelope.  You should just start to feel uncomfortable, but still be able to maintain the pace without too much difficulty.  Figure out what HR that is and set that as the top of zone 2.  If you want to find the bottom of zone 2/top of zone one, multiply that number by .93.  Those numbers won't be as accurate as actual testing, but they will defineatly give you a solid range to be targeting.  With that method, I would stay in the middle of zone 2 for most of your workouts. Use zone 1 for days you are recovering (so the day or so after a longer ride/run) or for days that you are increasing the distance you are going.  Does that make more sense?  If you want to use this on the bike as well, then repeat the test on the bike.  Your bike HR will typically be 8 or 9 BPM lower then running.

3) total immersion swimming is a teaching program.  They offer books, videos and drill cards.  Their aim is to help you build balance and form in the water.  This is their website: http://www.totalimmersion.net If you want to start working on stuff now, look at the second link in my sig.  There are a few drill in there that are pretty much identical to the TI stuff.