Nima,
Since you will test the upgrade first, you can use the regular install/upgrade page. It executes the same code and I have never heard of a callback problem. (Malte, if there is such a problem, please document it, file a bug and we should get it fixed.)
Nima,
The path to the APM is usually through a link called "Developer Admin". If you try the APM installer you will see it allows you to do some additional things, such as: force install if dependencies are not met or skip installation of SQL datamodel files. Obviously one would not want to try those things without knowing what was going to happen, but in most cases normal users installed a released version of OpenACS would not need to try that.
