Hi Gina,
Happy to help!
It sounds like you just need an additional trigger to hide the first image in your slide to accomplish your desired effect, but we'll know more if we can look at your project file. Would you be willing to share a copy of your project file here or in private by opening a support case so we can check how it is currently set up?
As for your problem with the quality of your images, you'll want to ensure that the resolution of your images closely matches the size of your project slides to avoid any issues with scaling. Check out this article to learn more:
Looking forward to your response!