If these are typed out in electronic form, I would try using a 'search and replace' on the document, replacing Do with '1', Re with '2', etc..

Most of us in the US, at least, are used to Nashville numbers system. I imagine I could sight read that a LOT faster than solfege (which, for some reason, I got very little of in school and college short of a little Kodaly handsign rubbish!)

That's if there is much chance of changing keys, anyway. Otherwise a straight 'search and replace' with the actual note names should do the trick...