The usual disclaimers apply: we don’t know each other, I haven’t seen your x-rays, I am secretly an agent for an inimical foreign power bent on shortening the lives of American citizens.
In a hiatal hernia, the opening in the diaphragm through which the esophagus passes is enlarged to the point that some portion of the stomach can slide up into the chest cavity; usually this is the part of the stomach that contains the gastroesophageal junction (where the esophagus connects to the stomach), but not always. Many people have small hiatal hernias and show no symptoms. There is not a 1:1 relationship between the size of the hernia defect in the diaphragm and the amount of stomach that protrudes into the chest. Not all hiatal hernias need to be operated on; only a few actually come to the attention of surgeons.
The main risk of a large hiatal hernia is that the stomach in the chest will become twisted and cut off its own blood supply. This is potentially fatal. Hiatal hernia can also contribute to reflux disease. The effectiveness of the muscles at the gastroesophageal junction (GEJ) that normally prevent reflux depend on the proper positioning of the stomach, diaphragm, and esophagus. Stretching and rotating the junction out of position compromises the sphincter function. If untreated for a long period of time, the esophagus can shorten to the degree that the stomach is not easily pulled back into the abdominal cavity. This is more likely when the esophagus is chronically inflamed due to acid reflux.
Surgical repair of a symptomatic hiatal hernia involves pulling the stomach down until the GEJ is back in the abdomen. The sac of peritoneum that has protruded into the chest is teased down into the abdomen as well and stripped away. The overly large opening in the diaphragm is cinched down, with care being taken to not close it so much that food will hang up in the esophagus. In virtually all cases, an anti-reflux wrap of some sort is then done to the stomach, for several reasons: one, 'cause the GEJ is abnormal and would allow reflux to continue even though the stomach is positioned properly; and two, to bulk up the end of the esophagus so that it won’t ride back up into the chest as easily. A few sutures are placed to tack the stomach to the abdominal side of the diaphragm as insurance. This surgery is normally done laparoscopically, with a few small incisions scattered over the belly. Virtually all anti-reflux surgeries involve attention to the diaphgmatic opening anyway.
Mesh is not normally used to close a hiatal hernia defect, because the hiatus has to be able to stretch to accomodate food and fluids entering the stomach. The edges of the mesh could also erode into the esophagus or stomach. Mesh may sometimes be used if the defect is so large that the edges can’t be brought together without tension.
This surgery is normally successful from a standpoint of keeping the stomach in the abdomen. Functional results may vary, usually related to how tightly the antireflux wrap is formed. Some patients complain of difficulty burping, nausea, early satiety, or food ‘sticking’. Results can vary between surgeons and institutions. In general, there is something of an art to balancing the need to tighten the GEJ to prevent reflux while leaving it loose enough to belch, vomit, etc. A patient’s symptoms post-surgery may not settle down to a final state for many months. The anti-reflux wrap may be effective for many years, but really long-term data (ie >20 years) is not available yet.
Going only by the information presented in the OP, I would point out that severe, sudden chest pains with dizziness (once CARDIAC issues are ruled out) in the presence of a large hiatal hernia can indicate torsion or twisting of the portion of stomach that is in the chest. This is a serious condition, potentially fatal, and can only be corrected surgically (it may be possible to untwist the stomach with a scope inserted through the mouth, but this is a temporary fix). If the hiatal hernia is small, this is very unlikely. Please follow through on seeing the appropriate specalist, who will likely perform an upper endoscopy to evaluate the condition of your esophageal/gastric lining.