What exactly happens before, during and after a Craniotomy?

Depending on the location, some scalp is flapped back and a hatch is cut in the skull. The tumor is removed. The hatch is replaced and secured with titanium wires. The skin is sutured back into place. The bone has no nerves so it does not cause pain. The skin can be anesthetized and the sutures can itch as it heals. I had a large tumor removed. Really had minimal post operative pain. I find blood draws more painful than neurosurgery.

Hello, your nervousness is understandable. Have you discussed this with your surgeon? Have alternatives to surgery such as radiation therapy been discussed? Have you or are you getting a second opinion? Surgery is often recommended if the tumor or over a certain size such as 3 cm.
My condition was not a typical meningioma experience because the tumor was large and was causing severe neurological problems. It was considered an emergency and removed three days after finding it.
Typically you will check into the hospital the day before surgery. You will have physical, and neurological testing and blood work. You will be asked your name and date of birth. A lot. You may be asked to shower using a strong antibacterial soap. On day of surgery you will be taken to a pre-op room. There you may be given a sedative and have some antiseptic applied. In the operating room you will be anesthetized. Your head will be placed in a clamping device to hold it steady. The hair at the surgical site will be clipped short. The actual procedure will be particular to your case. I won’t provide detail here. There are many videos available on YouTube if interested. The duration of the procedure usually ranges from a few hours to over 12 hours depending on complexity. My surgery took 4 hours including time to anesthetize. After surgery you will be woken up and taken to a recovery area. You will be given pain medication if you need it. My experience was pretty pain free, just used Tylenol. You will be taken back to your hospital room. You will probably be sleepy for the first 24 hours. You may have to sleep on your back with your head propped up. You may have a drain at the surgical site which will be removed the next day. I had to go to a neurological rehab facility after surgery so my total stay was 19 days. Typically you will be released 3-4 days after surgery. Time to total recovery at home will vary depending on your physical condition before the surgery. I recovered rapidly from the neurological issues and was back to normal activity 5 weeks after surgery. Depending on tumor grade the surgeon may recommend follow-up radiation treatment and regular MRI scans. Sorry for the book length response. Hopefully this helps.