Well now I was pleasently surprised to see how easy this was. Created a mjp file for the new DRM free walmart music download. Here's the code from the file I created and installed. Sweet!
<?xml version="1.0" standalone="yes" ?>
<MJPF version="2.0">
<Package>
<Name>WalMart</Name>
<Action>NONE</Action>
<URL>NONE</URL>
<Version>1.0.1</Version>
<HasActions>1</HasActions>
</Package>
<Actions>
<FileEntry>
<File>*.*</File>
<Action>
<Command>COPY_PLUGINDIR</Command>
</Action>
</FileEntry>
<FileEntry>
<File>*</File>
<Action>
<Command>REGISTRY</Command>
<Param>HKEY_LOCAL_MACHINE|SOFTWARE\JRiver\[NameWithVersion]\Plugins\Services\WalMart|AccessURL|http://musicdownloads.walmart.com/catalog/servlet/MainServlet</Param>
</Action>
<Action>
<Command>REGISTRY</Command>
<Param>HKEY_LOCAL_MACHINE|SOFTWARE\JRiver\[NameWithVersion]\Plugins\Services\WalMart|DisplayName|WalMart Music Store</Param>
</Action>
<Action>
<Command>REGISTRY</Command>
<Param>HKEY_LOCAL_MACHINE|SOFTWARE\JRiver\[NameWithVersion]\Plugins\Services\WalMart|IVersion|4</Param>
</Action>
<Action>
<Command>REGISTRY</Command>
<Param>HKEY_LOCAL_MACHINE|SOFTWARE\JRiver\[NameWithVersion]\Plugins\Services\WalMart|LargeImage|[PROGRAMPATH]\Plugins\WalMart.png</Param>
</Action>
<Action>
<Command>REGISTRY</Command>
<Param>HKEY_LOCAL_MACHINE|SOFTWARE\JRiver\[NameWithVersion]\Plugins\Services\WalMart|SmallImage|[PROGRAMPATH]\Plugins\WalMart.png</Param>
</Action>
<Action>
<Command>REGISTRY</Command>
<Param>HKEY_LOCAL_MACHINE|SOFTWARE\JRiver\[NameWithVersion]\Plugins\Services\WalMart\Treeitems|Purchased Music|[media type]=[Audio] [comment]=WalMart ~sort=[date imported]-d</Param>
</Action>
<Action>
<Command>UPDATE_SERVICELIST</Command>
</Action>
</FileEntry>
</Actions>
</MJPF>