new owner questions

Forgive me if these are dumb questions, but as a new owner - '75
Sundowner, I'm learning as I go here..

1. If I install a panel mount intercom myself, I need an A&P to agree
to sign the log. True?

2. My nav indicators are a King KI-204 with glideslope and an old
KI-201 or something that is like 30 deg off (2 KX170b's). If I buy a
KI203 on Ebay to match the 204, is it as simple as popping out the old
indicator and pushing in the new one.. will the pins match? Or is this
something I just leave to the local avionics guy?

3. If I replace the wing root seal, do I need an A&P signoff?

Thanks for any help.