It would normally require a demux, re-encoding by an MPEG encoder with the ability to change standards and then putting back together with a suitable authoring tool. It would be quite a job!
Only you can decide whether it's worth your while collecting the necessary tools together and then going through the learning curve needed to co-ordinate everything. I do have those tools and wherewithal, but I wouldn't dream of doing it unless the DVD was of great value and impossible to obtain as NTSC by any other means. Frankly, I'd rather buy new DVDs.
Anyway, are you quite sure the Sony doesn't deliver. Most players output NTSC from NTSC discs (or a sort of quasi PAL) and PAL from PAL discs. Then it's up to your TV to make sense of it. Most newish European ones can...?