No, first stop at the local public library. These businesses go to cemeteries on a regular basis and they may have a map of the cemetery plots. They may also give you better directions to the cemetery. At the funeral home, ask if they have records dating back to your ancestor's burial. These files sometimes include obituaries, next of kin, place of death, etc.
Funeral directors are usually very helpful and are an overlooked source for records.
Cemetery monument companies don't usually keep the same type records as the funeral homes. They are more likely to give you other information such as road condition to the cemetery, the overall condition of the cemetery, or the name of the caretaker or association who looks after the grounds. The Big Tree Technique is very simple and should be tried if you looking in a small cemetery. If you don't find the grave, use the base of BIG TREE as your starting point. Using the base of the tree as a starting point then search the surrounding plots in an ever-widening circle.