here are some updates...
a. I guess a sound card / mixer would help. My motherboard has a mic-in for which we can select the function... It will either work as a mic or as line-in... Whenever I plug in a male plug, i get an option to either select mic-in or line-in... But since I would want to use both of them together, I think I will need a mixer / sound card....
b. Got the answer... a prog like FL studio would help...
c. Still researching....