Here's the full list of what I replaced:
Coin door bulb
Sticks + Buttons
Coin reject button
I love this thing. I have 5 games for it now (Metal Slug 1,2,X, Puzzle Bobble, Baseball Stars 2), with 5 more coming (Last Blade 2, Samurai Showdown 2, Blue's Journey, Blazing Star, Neo Turf Masters). I'm beyond happy.
I also added some Ikea shelving to hold all of my controllers. Very nice. Here's a pic of the room as it looks now:
One of my Xmas gifts was the official Dreamcast Arcade Stick, which can be seen on the shelf. It makes playing Dreamcast fighters much more enjoyable than using the stock controller, which I'm not a fan of. I need to get another stick for 2-player fight sessions. Highly recommended. I may swap out its stick and buttons for Sanwa ones, but that's another project.