Removing old part

I have my new 90-115 keeper, but I am having difficulty removing the old part. It looks like it should just slide straight up after removing the screws, but it's stuck. Any tips on how to loosen it?

Never mind - I squirt some 3-in-1 oil everywhere I could, and after much wriggling it finally came out. One down, four to go!

OK, my first problem pales in comparison to my new one. The keepers on the bathroom window had rusted (which allowed the burglars to break them,which is why I ordered replacements.) Unfortunately, the keepers broke inside the window. I can get the top part out, but the bottom, below the holes, is still inside. I think I may need a different kind of lock. Any suggestions?