Training for distance, suggestions?

Hi everyone, I have been more off the forum than on due to no internet in our home anymore; we are researching options. Anyway, I just wanted to mention that I started training on January 15th and am about a month into my training now. I am primarily training to do a very long swim, 18-19 mile ocean swim, in August of 2008. So I thought because of my age, 59, I needed to start small and increment slowly. Here is where I was a month ago and where I am now, both in distance and time, and wanted to see if anyone here had any suggestions. I swam M-W-F from Jan.15 until last week. I have now added Saturday to the mix. I started out swimming 1,000 yards each of those days and suffered greatly aerobically (the word physical fatigue comes to mind). Two weeks ago, I went to about 1500 yards each workout. The reason for this slow start is I previously had two shoulder surgeries and I wanted to make certain the shoulders would fare well. They are fine. I have made Wednesday and Saturdays distance days. Last Wednesday, I swam a full mile for the first time since Jan.15 and swam a 28 plus. It wasn't the time, it was how bad it felt; still not aerobically sound yet (ouch big time). On Saturday, I did my first 2 mile non-stop swim and it felt wonderful during it. My time was 54:02 and I am pretty happy with it so early on. My biggest problem with the 2 mile swim was this: my neck was sore from turning it to breathe!!! This was a surprise. I had a stiff neck Saturday and Sunday. Today I only did a one mile swim because the ocean was angry and there was horrific current and waves. As I crested one wave, it literally slammed me down on the water; I was actually airborne for a brief moment. Feels pretty weird kicking and stroking in air (LOL). So, now that I am almost a month into training, I do a mile and a half on Mondays and Fridays and include sprinting and drills on those days. On Wednesdays, I do two, one mile swims with a 1 minute break. On Saturdays, I double the distance at a minimum. This Saturday, I will do another straight 2 mile swim or 3 mile swim; will decide that day. I will be swimming in the 2007 Bay Islands International Triathlon here in Roatan on March 18th. I will be the swimmer on a relay; my other teammate is an Ironman competitor from North Caroline and he is doing both the run and the swim. There is still time to register if anyone is interested. They have multiple distances since it is also Pan American. If anyone has any suggestions as to how I can better or differently train to get myself upwards toward the 5 mile mark or further, I would welcome your experience. Once at the 5 mile mark, my conditioning will be relatively fine-tuned to endure longer distances. I will probably only take about 2 days rest before the triathlon March 18th since I am not in full-blown condition yet. Does this little taper sound about right? Donna