I don't think the question is really well formed. An ability to change my DNA sequence (with or without any of the accompanying epigenetic stuff) doesn't imply any ability to predict the effect. Somebody already pointed out that an awful lot of stuff has to be done at specific points in development. I'd like to add that we have zero idea what 95 percent of the genome is doing, and probably no complete idea of what any of it is doing.
In principal, you could come up with alterations that would cause you to "regrow" into any new form you wanted. In practice, you might have to be a god to figure out what changes to make.
If I were given the ability to modify any part of any sequence at will, but stuck with the present state of knowledge of the actual effects, I'd go do a ton of research to see if there were any clearly known predispositions to disease that I could fix without too much risk of nasty side effects.
If I answer the question in the spirit of "how would you modify yourself given the ability to make any change you wanted", I'd start by giving myself the built-in ability to make further modifications at will, without outside equipment or help.
Then I'd start throwing in "superman" stuff at whatever rate my sense of identity seemed to be comfortable with. Probably starting with better resistance to disease and damage, and better healing. Then smarter-stronger-faster, better senses, etc. Lather, rinse, and repeat until thoroughly posthuman.