I own a 1973 T30 (hull #173), and have overhauled it extensively (everything from hand painting new LPU on the mast, boom, decks and non-skid to replacing the atomic 4, fairing blisters, etc.). They are great boats, and I enjoy mine immensely (although I'm putting it on the market due to a relocation). Has been a fun cruiser and is fairly quick and sweet when sailed properly.
For a very comprehensive overhaul narrative, google search for a great blog called 'tartan30makeover (I can't paste links yet...)
This guy went nuts on his boat - beyond even what I did to mine. The results are stunning. You might get some good insight into the inner workings of this boat there.
There is also a fairly active owners group that has good articles and resources, tartan30 .org.
Best of luck! IMO if you enjoy the process of upgrading and working on boats the T30 is itself a good place to start, and the end result will likely be something special (at least to you...)