Channel Guide for older DirecTV receiver box - D12-100

I am writing this post on behalf of my grandparents, who are very far from tech wizards.

They have DirecTV service in their home with an HD box and all current equipment (to my knowledge).  They also have an old d12-100 box they use at a hunting lodge for television; they used to have it for ages at their house and then took it to the lodge when they upgraded.

I know the D12-100 is ancient by today's standards and I'm sure I'm opening myself/ourselves up to jokes.  Any attempt we have made to upgrade the box has been met with DirecTV telling us we need to use a box that requires a constant internet connection.  This hunting lodge has no internet, nor would it be possible for us to get broadband internet access at the address.  This is a rather isolated piece of property.  So simply upgrading the equipment to current spec is out of the question.

He has an old channel guide at the lodge, but wants an updated listing.  However, when I look up channel listings, it's all for current boxes that receive HD channels.  Some of the channels listed, even though it's the correct package, are not received by the D12-100 box.  I would go through and just not list channels with "HD" by them, but he does get feeds for some of those channels.  Example:  He does receive Comedy Central and ESPN, despite those being listed as HD channels, but there are some HD channels he doesn't get at all. 

I would do this the hard way by going to the property, taking my tablet, and making a chart of the channels he does get one-by-one, but the property is a pretty long drive down and back.  If I can save gas by not going all the way there just to see what channels he gets, that would be a lot of help.

Is there a place where we can either find the channels this specific box has available? OR is there a way we can upgrade the receiver he has without upgrading to one that requires an internet connection to function?