To be honest, I think that if you look at 'conversion' as a process of re-imagination.. So that you take the clearest aspects of your characters, their strengths and weaknesses, the roles they like to play, and their backgrounds. Then you apply them to the 4E options, and take your closest fits.
To accurately represent the power level you are now maybe be difficult, and will change, and your DM may or may not have a large amount of work cut out for him. I typically draft my encounters very lightly, so I'm not anticipating a large amount of extra work, in terms of conversion.