What type of your industry is? What is your finished product or service? What is your designation? Does this HR intervention has sanction of top management? Are they aware of the quintessence of Performance Appraisal (PA)?
As far as introduction of (PA) is concerned, it is larger part of Performance Management System (PMS). Therefore, I recommend you to introduce comprehensive PMS rather than introducing just the subset of it.
If you are new to PA then you need to hire external consultant. [i]Studying systems and processes of each department, identifying direct and indirect costs of each department and then designing KRAs on each cost requires tremendous amount of maturity and if it left to some external consultant the better. Please note salary hike is not the only aim of PMS. You can bring major cultural change the company by introducing PMS based recruitment, training, career planning etc.
I have been giving my posts on introduction of PMS time and again. You may click the following links:
If you wish to know more about my PMS consulting services then you may click here
Dinesh V Divekar