In the wmsUrl variable, you are missing the "http://", that may help. Pink tiles generally mean that the data source was not found, so this is where you should look for the problem. Try checking the wms URL you are supplying in a wms viewer (e.g. ArcGIS Explorer ).
To your questions: 1)try just adding the http:// to your url, without the localhost
2)A WMS layer can have any projection, it depends solely on the projection in which it was published. Information about a specific WMS's projection should be found in metadata.
3)If the two layers have the same projection, you do not need to do anything. If you want to use two layers in different projections in one map, one of the layers must be reprojected. In pure OpenLayers, this is done by specifying the projection parameter for each layer and then specifying the displayProjection parameter for the map. The layers will automatically be reprojected. However, reprojection takes some time and it increases the load time VERY significantly. It is better to avoid reprojection on-the-fly, if possible. You can either reproject the source data of one of the layers and use reprojected data. Of course, this is not possible for a WMS, so you should consider using a different data source. If you want a background map, you can donwload OpenStreetMap data, reproject them to your desired projection, and then use them with the other WMS you want to use.
Hope at least some of this helps :-)