Can I replace a photo without losing my hotspots?

Yes. On the Panoramas tab, select the scene and click Replace Original File, then add the new file on the Upload New tab: it goes into the same panorama, so its hotspots and each tour's settings for the scene stay. Every tour that uses the panorama gets the new picture, and there is no undo. A tour with Draft Workflows on keeps its published page, which still names the old picture, until you click Publish changes on it. The Asset Library tab in the same window swaps in a different panorama instead. That does not carry the hotspots over: the scene then shows the other panorama's hotspots, and yours stay with the old panorama. Replace or swap a panorama's picture has the steps.