Yes. Sciatica is typically caused by a lumbar disk herniation. When the disk herniates, it compresses the nerve causing symptoms. Surgery removes the compression by removing the herniated disk. As long as the spine is stable, the back doesn't need fusion. Additional compression can be addressed with a laminectomy.
Yes. Sciatica, which refers to pain radiating down one and sometimes both legs in a particular distribution that corresponds with the sciatic nerve and its branches. This usually occurs at the level of the spine at one or multiple of the nerve roots (usually l3-s1) that come together to form the sciatic nerve. Surgery is not always indicated and certainly is rarely a first line treatment.
Speak with surgeon. He should be able to address your concerns about surgery.