Looks like you already have the handlebar clamp bolt removed. Just need to work (twist) the handlebars in the clamp to release the rust, then you can slide the bars out to one side and put in the new bars. For the stem, if the bolt is already out, put it back in about 3-4 full turns. Should have some bolt still not bottomed out, and then you can tap on that bolt to release the stem clamp.

Penetrating oil might also help both areas. Apply generously down the stem bolt hole (put a rag underneath to catch the overflow). Around the handlebar clamp will help, but you can probably just twist them.

After using the penetrating oil down the stem....you'll need to completely clean out those areas/parts, and then regrease.

HTH.