The real difference is the effects level control, basically the CE-2b mimicks the sound of the CE-2 real well with this control fully clockwise (full effect - no clean signal).
There's also a little difference in the frequency band the chorus works on, but either pedal sounds great with both instruments.
Why do you want to mod the CE-2, those are mostly fine as they are.
My wife uses the CE2B on her bass (in fact it's still the only effect she uses on her bass).
I've tried the CE2B with a guitar (in a direct comparison with a CE5 and CE20)... I prefered the CE20, or the CE5. The Bass mode on the CE20 is not the same as the CE2B either (the CE20 adds just a hint of flanger to the chorus).
However, I tried the same chorus pedals with the bass and the CE2B was the better of them.
Why do you want to mod the CE-2, those are mostly fine as they are.
because every time i press the pedal nothing comes on sometimes. dont get me wrong it works but sometimes it doesnt and thats very unreliable to me so im gonna have it modded to see what the problem is because im not a electrical guru like most people on this fourm, i dont even know how to soder but i will not get rid of it as i know i would regret it