Getting around Osaka?

My husband, daughter, and I have a 7 hour layover in Osaka Japan and wanted to spend a few hours sight seeing. I've looked into a personal tour guide since we speak no Japanese, but can save some money if we go off on our own. We wanted to go the the castle, the park around it, and eat lunch. Will it be easy for us to get around via subway and eat somewhere? I'm really good about doing research, so I can look up what trains to take and which stops to exit. So pretty much do you think we will be ok getting around with no knowledge of the Japanese language? Any tips would be helpful. Thanks!