Alright:
<img>http://www.jpdawson.com/creation/celltrz.gif</img>
So, abiogenesis aside, you have your single celled organism. This is where I find a flaw.
What are the chances that this single celled organism is asexual? One out of three.
Three out of three.
And what are the chances that this cell knows how to split and reproduce, if it was asexual?
Cells don't "know" anything. They just do things. And one of the things they do is reproduce. Reproduction is one of the characteristics of life. A living thing doesn't have to learn to reproduce. If it did not reproduce it would not be classified as "living".
Single celled organisms aren't very complex,
But some are more complex than others. You might look up the difference between prokaryotes and eukaryotes.
Also the theory that eukaryotes came about by symbiosis.
Also keep in mind that you get a lot of diversity over a lot of time long before you get to multicellular organisms. We tend to overlook the huge amount of diversity in unicellular organisms just because we don't ordinarily see them.
For about 2 billion years we have diversification of prokaryotes before we have record of eukaryotic life. And then we several hundred million years of more diversification of both prokaryotes and eukaryotes before we have any record of multicellular life. For 90% of earth's history there were no multicellular organisms. All of the rest: all the evolution of plants, fungi, animals of all sorts took place within the most recent 10% of the history of life on earth.
so tell me how you think it went from a single celled organism, and then reproduced, and so forth.
There was probably more than one way this occurred. The link in molal's post shows of one way it could happen.
As for reproduction, it is likely that at first organisms switched back and forth from being unicellular to multicellular. (check out slime molds for an example of this) and gradually evolved the reproductive methods we are more familiar with.
So, now we have covered the fact that:
--all living things reproduce; this is a fundamental characteristic of life, not something a living thing has to learn.
--we have lots of reproduction and diversification at the unicellular level for billions of years before we have multicellular life. This includes the development of eukaryotic cells.
--we have at least one example of how single-cell organisms become multi-celled organisms.
--we know of several different modes of reproduction, including some that straddle unicellular and multicellular life.
Now, what was that flaw you were speaking of?