Yes a laminectomy is a major surgery.
Although most laminectomy surgeries go smoothly without much if any complications there are still potential complications and risks associated with the laminectomy surgery.
Some risks and complications that come along with having laminectomy surgery are things such as spinal fluid leak, nerve damage, blood clots, bleeding, infections, worsening of chronic back pain.
There's also some risk associated with the anesthesia that you will be put to sleep with.
But most laminectomy surgeries go through just fine and many people who have the laminectomy surgery come out of it without any problems.