Will replacing just the o rings fix this and is this causing a vacuum leak?

 

There is no way for us to know if just replacing the O ring will fix your problem entirely. I would think the tube should tighten down whether the O ring was there or not. You may have bad threads on the tube. I used to clean and silicone mine in place to help it seal.

It can allow air into the crankcase and lower the vacuum level. This can cause an oil leak in other areas. It can also allow dirt into the system. It can also cause oil to be sucked into the intake. It is critical to maintain a healthy vacuum level in the crankcase.

Believe it or not, the number one cause of oil leaks is not a leaking seal or gasket but a poorly performing PCV valve.