Without access to the specific mechanics of the Dragonmarked feats, it would be difficult to play such a character. If you cannot gain access to the 4e Eberron books, you most definitely can still play, though you will not be able to use the mechanics available in those books. Here's my suggestion (and the greatest bang for your buck):
Subscribe to D&Di; You will gain access to the Character Builder, which has pretty much everything you could need to build a character. Although it is always a month behind on products, that's not a long time to wait to see it in the builder. Simply configure the Character Builder so that the only available options match the LEB charter and BLAM, now you have an LEB character generator! I don't know if this is an option (due to the cost) but it's an idea!
Also, as far as the Grand History of Eberon is concerned, the creator has given credit to all of those who are due credit, and has even had contact with Kieth Baker about it. No need to worry about legalities there! There are NO mechanics at all in the Grand History, just background and history of the world, complete with chapters for each of the houses! The perfect way to get a feel for the world is to first get a base idea of WHAT and WHO is in the world (especially Sharn, since that's where you start!) and then to play in it. No need to memorize the Grand History (I know I haven't), just peruse it and learn what you WANT to learn about the world. It's especially great for DMs as it's got entries for each of the main locations/countries.