You probably want to bring in some of your datasets and merge them with the projected schema. Copy and paste is the easiest way to do this, but you may get some error messages about differences in the source/target spatial reference. For example, when you try to copy and paste in ArcCatalog you may get messages like this:

This is due to some subtle differences in the properties of the target feature dataset/spatial reference and should not be a concern. The best way to handle this is to use the Import Feature Class tool in ArcCatalog:

You can also use the equivalent Geoprocessing tool: "Feature Class To Feature Class".

In ArcGIS, Geoprocessing (GP) tools and scripts can be used to do the data manipulation and loading tasks. At a high level, the process involves using GP to massage the source data until it matches the data model of the target geodatabase, and then using commands like Append to get the features into your target geodatabase. This works well for most data loading situations, especially if you using Python or other scripting tools for automation. Once you figure out the pattern you can copy/paste scripts and blocks of code and it is generally easier to manage than ModelBuilder Models for data loading.

Example:

Another option is the ArcGIS Data Interoperability Extension. This extension provides a visual workbench to connect source and target datasets, and has a useful set of tools called "transformers" that can be used to perform calculations between source and target (for example, LifecycleStatus should be a new field called ACTIVEFLAG and LifecycleStatus="Active" should be ACTIVEFLAG="1"). This approach is preferred by many specialist users but does have an associated cost and learning curve.

Examples:

Simple Example for wFitting, similar to the Python script for wCasing.

Portion of more complex Spatial ETL tool example for wMain

Sample Tools