I have been working a lot on my free time on this and here is the current progress:
Progress has gone down since last time. This is a little more accurate than my last estimate. The coding is almost done, I have a few major features I would like to add before I get any farther on anything else, and some small tweaks, bug fixes over and over. The music and sounds, I redid the sound manager with Alumiun's advanced sound manager, so now I have my music in MIDI rather than IMF format. I am also composing all of the songs myself. The sounds are all done, giving room that I may add some in before the game is finished.
The maps are moving very slowly, but they are going swiftly in the past week. I have the first 3 maps completed, a few enemy placements, health, etc to do yet. Most of the levels in Episode 1 have been started. The later episodes have not been touched yet. All of the images have been put in besides the ones for a ViewWorld feature I have not yet installed. Similar to the one you see at the end of every level in DOOM. I have made it before, not too hard to put in.
As for the walls, objects, sprites. All done, except for new bosses I would like to make myself. I wish I could get all these things done before I finish the maps but I have been trying my best to do it all in moderation. The hardest things to do will be making the music, finish the hard code changes, new enemy sprites, so that will be the reason the game will take a long time to create. So it is far from being complete at this point. I would like to finish it within the next year or so, but only time will tell.