There are many different maturity models for project management. One popular one from IIL's Dr. Harold Kerzner includes 5 levels that parallel the SEI CMM model. The OPM3 Methodology provided by PMI does not support the notion of levels but rather offers continuous improvement over a number of dimensions. So knowing what you are trying to achieve is important. If you leave a comment I will contact you back to continue the discussion.
In general, no matter model which you choose, PM is not overhead but a practice that brings value to and improves the financial statements of companies at almost every line.