Quoted from CreepyTom:Just joined the club today, are there any must have mods I need to have to enjoy the game? I plan on having it for a long time.
Color DMD in Scan mode really enhances the game a lot. I think the Shire Decal is much needed as that part of the playfield is so barebones without it. I'm also a fan of the Army of the Dead mod to add some character to that upper playfield. As stated above, the palantir mod is incredible but almost impossible to find. A new person is making them now but there's a back order list of at least a year already, and we don't even know if enough parts exist for him to make them all.
If you're into enhancing the art, there are some really great options for art blades: sillyoldelf's are my favorite, but there are also brass mirror blades which are cool and a few other art blades including ones that light up.
All in all, it's a great game. I'd suggest just giving it a good cleaning and enjoy the game.
EDIT: LEDs are controversial on this game, but IMO if you do them tastefully they really add to the game as well. You need to use an LED OCD though which is not cheap. Don't try to do LEDs without one, there is too much dimming in the game that will cause LEDs without the OCD to just flicker too much.