I fingered it out. Thanks for the views. The following code will ask for a prefix string then loop through the existing user parameters and rename them. I will work on the if existed at a later time
Dim i As Integer
Dim oTempString As String
Dim oDoc As PartDocument = ThisDoc.Document
Dim InputPrefix As String
Dim myparam As String
Dim NewName As String
If oDoc.DocumentType = kPartDocumentObject Then
Dim oPartCompDef As PartComponentDefinition = oDoc.ComponentDefinition
myparam = InputBox("Enter Prefix", "Prefix", InputPrefix)
Try
For i = 1 To oPartCompDef.Parameters.UserParameters.Count
oTempString = oPartCompDef.Parameters.UserParameters(i).Name
NewName =myparam & "-" & oTempString
oPartCompDef.Parameters.UserParameters(i).Name = NewName
MsgBox(NewName)
Next i
Catch
MsgBox("Parameter " & oPartCompDef.Parameters.UserParameters(i).Name & " could not be renamed to " & myparam & oTempString & vbCrLf & "Please check results.", MsgBoxStyle.Critical,"Rename User Parameters")
End Try
End If