ye you'll need a mixer you can find a 4 chanel one quite cheaply on e-bay but then it depends what you wonna do with the recording.
1. the recording that you take cannot be modified, so you cant change the timing if you don't like it
2. if you wont stereo sound you need to make sure that the mixer is stereo and that you sound card can take stereo.
3. if you wont to edit the sound for voice overs or your recording music you should record each sound buy its self so that you can later edit the flow of things in a sound editing package like adobe audition.
hope that was helpfull