You know, a lot of professional manga just have a subtitle next to the SFX, instead of completely deleting the original characters and replacing it with English in the same style (Viz does this one, mainly)... so it would probably be a lot easier/far less stressful to just put the English translation next to the JP sfx!
Should keep that in mind if it ever gets to be too much to completely redraw all the SFX in a chapter.