Iphoto Issues

I updated to Yosemite and have a couple of issues. I will go through the responses I see others have gotten to solve one of the issues, thank you. My actual dilemma is that I have photos for our museum with descriptions, keywords, etc and now I don't have access to any of that. When I click the icon for iphoto I'm basically told that in doing so I will screw up my photos.....I'm sorry but Apple already did that for me and I don't want to do any further damage.

Yes, I have a photo backup and time machine but neither are of use if I can't get the descriptions and everything else to transfer to the "new" photos app. The ability to add all of that detail as well as edit and then print the information along with the photo was a fabulous feature; you truly had such a great thing with Iphoto so I don't understand why is it that when you've got something good you have to change it completely so as to make it useless. If it isn't broke why "fix" it.

Will the new photo app function the same as the iphoto app or....do I now have to buy a new app, how much will that cost.....and which one must I buy to function the same way?