Global Rail Pass Include City Metro?

I would not think so. In order to board the train, you need a magnetic strip ticket or Navigo chip card to open the turnstile. You also need that to exit the station. I could be wrong. You would need to spend time at the CDG station and get your pass validated, maybe they'll give you a mag-ticket. Fine print on the Eurail site should say what and what is not covered.
However, you can bypass Paris by going on a route that goes around Paris either to Champagne-Ardennes TGV, Loraine TGV, or Brussels, then to Luxembourg, then to Trier. You will have to pay the TGV surcharges and be subject to their pass holder limits.

Rail passes do not cover local transit or private rail lines.

Just so you know, the fare into Gare de L'Est is more like 9.50 euro, since you are taking the RER B to Gare du Nord, then walk to Gare de L'Est or hop the Metro for one stop.

Before you decide to plop down far too much money for a railpass, please read any of the countless threads that discuss passes. But for a short summary... they do the exact opposite of saving you money and they aren't nearly as convenient as they used to be. Procede with caution.

Tom is correct. Twenty years ago prior to the internet, capacity pricing, load management, advance discounts, etc., the rail pass was a no-brainer, good deal. In today's markets, you need to burn a lot of brain cells determining if the pass will save you money for your travel schedule. Have to do the homework and the math.

"Rail passes do not cover local transit"

Just to clarify, in German cities, the S-Bahn is a train of the Bahn and consequently covered by a rail pass. The other conveyance in cities, U-Bahn, trams, and buses are not covered.

As for France, I believe, but cannot verify, that the RER line from CDG to Gare du Nord is the only RER line in Paris covered by a rail pass, and only from CDG to Nord. If that is still true, Gare du Nord and Gare de L'est are next to each other, so you could walk between them.

Note, I think the pass benefits page for France on eurail.com used to say something about the RER use in Paris, but it no longer does. Eurail.com does, however, mention S-Bahn being covered in Germany.

"I wouldn't use a day on a very expensive pass for just a quick RER ride into Paris from CDG."

That occurred to me too, but the OP says they are going on to Trier from Gare de L'est, so, if they are using a railpass anyway, it would be worth using the RER option. My advice, unless it would change your plans (like you would walk to Est if you could not use the RER as part of your pass), just plan on doing it and ask at the RER desk if it is covered.

I haven't found a pass to be cost effective, or used one, since 2000.

If you do decide to use your pass on the small covered portions of the RER you need to find a manned entrance so they can buzz you through the gate. They will also have issue with a "Contremarque de Passage" so that you can get out the exit gate. A Contremarque de Passage is a magnetic ticket which opens the exit gate.

To be honest, it is usually more trouble than it is worth in many cases.

The difficulty comes with the small sections of the RER where control of the trains switches from SNCF - where the pass is valid like on other SNCF areas - and RATP, who run the Paris Métro on whose patch the pass is not valid.

I use a different pass (not available to the general public) on which I have received the following advice:

• RER Line A – SNCF from Nanterre Préfecture to Poissy or Cergy-le-Haut.
• RER Line B – SNCF from Gare du Nord to Aéroport Charles de Gaulle or Mitry-Claye.
• RER Line C – SNCF in its entirety.
  
• RER Line D – SNCF in its entirety except between Gare du Nord and Chatelet les Halles.
• RER Line E – SNCF in its entirety.

Your results may vary.