Hi Wayne,
Each table in Method contains the RecordID field. This is a required unique field for which the value is generated by Method. The reason this field exists is to differentiate a record from other similar records if for some reason the table does not contain another unique field.
When a dropdown field is added to a table, the RecordID field from the dropdown’s table is linked as well, in order to retain a unique identifier. Since this is a linked field, entering a value into it is not necessary. The SalesRep_RecordID value will be inserted automatically based on the value that you enter into the SalesRep field. That is, you do not need to import a value for the SalesRep_RecordID field. The same applies to the CustomerType & CustomerType_RecordID fields.
We do have some documentation on using the Import / Export tool in solution No. 189 of our Help Center. We also have a couple of blog posts that detail importing customers and contacts. These should give you an idea of how the import process works and provide you with a basic understanding of table relationships. You can find these here and here.
If you have any follow up questions, please let me know. I hope this helps.
-Audisho