Hi and thanks
You can use one of several 'decompilers' to extract the models from a file. You should not attempt to modify a stock Bgl file.
For example BglAnalyzeX (available from the downloads section here) or Bgl2Xml ( )http://www.mediafire.com/download/kv3x6uzsk2tk1yd/bgl2xml_137.zip )will extract and save the models in a library Bgl file.
You will then need to use a tool such as Library Creator XML (in the downloads section here or from the downloads section of www.fsdeveloper.com)to put the models into a new library without placement data. Support for Library Creator XML is available from www.fsdeveloper.com and there are many knowledgeable folks here who will know how to use that tool.