MC 3.05, Dell650, analog Mojo.

Do I need extra audio recording hardware to get a microphone signal into Avids punch in?

Or do I just plug the mic into the built in mic input on the computer, would the sound quaility be acceptable for tv?

Or the mic directly into the Mojo cinch (quality?)?

Could I use Cubase (they sell an XLR to USB device, including the program) to directly record within Avid?

To record punch in you have to use the Avid software.  You should be able to by pass the Mojo and go through the computer line in or connect to the rca in on the Mojo.  Going through the Mojo is probably the easiest plan.  Either way you will have to go to your Audio Project settings in Media Composer and go to the input tab and select RCA or whatever you are using

I´m concerned about quality.

Mojo doesn´t have a specific mic input, I´m not sure if I can plug the mic directly into Mojos cinch audio input and get a decent sound quality.

Is it worth buying extra hardware to improve sound quality?

I have always had to use some sort of mic pre-amp when using punch in with mojo.  at our studio we have an old mackie mixer that still hangs around for that purpose alone.  I'm pretty sure a basic pre-amp can be found for 50 bucks or so.  Avid's own M-Audio has a 50 dollar audio buddy that moght do the job.

The pain with mojo is that you'll have to convert your balanced audio signal to an unbalanced audio signal that's -10db quieter, thanks to the phonos in on the mojo. If you're concerned about about quality, I suggest you get a secondhand audio mixer - something small with only a couple of mic pre-amps will be fine. Then run your mix out into a line balancing transformer (like a matchpak or an alice) which will convert to a suitable level for your mojo audio ins.

HTH