Woah, what a beauty!

I'd say it's mid to late 50's. I have one from 1954 that looks somewhat more primitive.

Anyway, to answer your question, under no circumstances should you repaint that. The paint and graphics look dang near perfect. If it had already been repainted, and there were nothing left to preserve, then my answer might be different. But as we see it here, you have a nearly pristine piece. Drysdale's bikes are rare, and examples in that kind of condition are very rare indeed.

Aside from that, let's say a repaint would cost you... oh, let's say $500. Maybe a bit less. When you're done, you'll have a bike worth about $500. Maybe a bit more, probably a bit less. But what you have now is worth quite a bit more, like two or three times that. Repaint makes no sense.

Cleaning it up, well, I think that would be fine.

Just out of curiosity, have you seen a serial number anywhere? Late 1930s Drysdales had the serial number on the back of the fork crown and under the bottom bracket, but mine, mid fifties, has none.