1) 32" TV seems a bit large for an arcade cabinet in my opinion. Most people like to go up to a 27" TV only so you will still be able to roll your cabinet through a standard doorway. I purcased a cheap 32Meg TV card with S-Video out and used S-Video to connect to my $50 JVC 27" TV (which has an S-Video port obviously).
2) I am about 80% sure that only the "Act Lab light guns" and "LCD Top Guns" work in Mame. Need someone to confirm though .... to be absolutely sure
3) Your pushbuttons are connected to a keyboard encoder. The keyboard encoder is programmed so each of those buttons are mapped to a keyboard key. When you press the pushbutton on your control panel you are then basically pressing the keyboard key.
Now, each emulator generally allows the user to set which keys they want for each action in the emulator (ie: Start, Jump, Kick, Gas, Brake, etc...). You simply set up the emulator with the same keys which you used as mappings for your pushbuttons. You should then be able to play the emulator games with your pushbutton. Each pushbutton has one switch, so you assign one keyboard key to each switch. Joysticks have 4 switches (up, down. left, right) so each joystick will require four keyboard keys to be mapped to it.
Worth mentioning ..... some keyboard encoders (Hagstrom KE72 encoders and perhaps the IPAC .... dont really know since I do not own an IPAC) allow you do remap the encoder by running an external application which comes with the encoder. This means when you change emulators, then you can remap your encoder to the emulator's default key mappings. This is handy for emulators which do not allow the user to change the default key settings.
Do you homework ..... read everything you can before starting so you know exactly what you want to buy and how it should all work together before purchasing.
WELCOME TO BYOAC !!!