custom item!

Hi everyone,
I want to add custom collectible items in the track. Let's say 'coins' for example which can be collected along the tracks. How can I go about doing this? Can it be accomplished through addons? Do I edit tracks? And do I also program the game so it recognizes these items? Can ayone suggest where I should start? Thank you all.
I want to add custom collectible items in the track. Let's say 'coins' for example which can be collected along the tracks. How can I go about doing this? Can it be accomplished through addons? Do I edit tracks? And do I also program the game so it recognizes these items? Can ayone suggest where I should start? Thank you all.