fix my website header with other Magento problem.

I have three small problems with my website. 1. The header is not displaying my logo and as a result the whole header looks bad. 2. My website is based on Magento, I recently had an Extension installed but the job was not finished, I want it fully removed. 3. This problem may be related to the second, I am trying to integrate Google Analytics to my website but the tracking number is not being detected. So there is no data being collected.