For double discs, just use the "Disc x of y" ID3 tag. It's already built in to the iPod and iTunes 3.
You'll still have to rename your tags so that the album name matches but you definitely don't need to renumber tracks.
Method: Select all the tracks of "Disc 1" and cmd-I to open the batch tag editor for the selected files. Then change the disc tag to "Disc 1 of 2" and rename the album without the "(disc 1)" suffix. Do the same for all of the tracks of the second disc.
Now iTunes will play all of disc one, then all of disc 2 in order, and "shuffle by album" will play the two discs successively as well.
Apple, the iPod Isn't Finished!