Patients in my practice that have very large breasts, such as you describe with a G cup size, are almost universally happy with breast reduction surgery. As others have stated, breast reduction does carry risks and of course a careful evaluation and consultation with a qualified surgeon is critical.
Breast reduction surgery uses incisions into the breast to remove breast tissue, support the breast in a higher position on the chest, and typically raise the nipple position to a higher level. Such surgery always leaves scars (with the exception being that some patients may be able to have a good result by reducing the breast using liposuction only through tiny incisions), and we cannot be sure what the quality of your scars will be before surgery.
In the vast majority of cases in my practice, I am able to limit the incisions such that the scars end up as approximately a "lolly-pop" shape around the nipple and areolar skin and a vertical scar below this on the lower aspect of the breast. Occasionally a more traditional "anchor" shaped scar is needed or even skin grafting of the nipple in extreme cases.
We have many before and after photos of breast surgery patients on our websites (we now have a site, ElegantBreast.com, that is dedicated to breast surgery) and have posted some to realself.com as well.
Hope this helps.