As far as altar calls go, I remember early on in my preaching, i used to gage the quality of my sermons by whether or not someone came forward during the "altar call". Seems so far removed from where I am today. I can even remember the looks of pity I would get if there was no response. After the service, I would here comments such as keep it up you will make a fine preacher some day, these comments were directly related to the response I received during the "altar call".
This
article by Jim Ehrhard was one of the first to move me away from the "altar call".
In a church where the Invitation System is deeply entrenched you will be hard pressed to make a change after only one year. Your primary focus should be to make the most out of what you got to use. You can continue to use the "altar call" and slowly move away from it in time. Just make sure you press the people hard about what true conversion is in the meantime. A sudden abrupt change will not benefit the congregation. Go slowly forward, preach the word, start with your leadership as you begin to show the more biblical approach.