There are some great suggestions above. Here's a couple of other things we found living aboard weekends during the summer and in the winter until it gets below 40 degrees.
Tackle boat smells. There will always be some water in the bilge, the shaft seal on the Catalina 30 is adjusted properly when there is a slow drip unless it's been replaced with a dripless seal. Vacuum both bilges (salon & under engine) with a wet/dry vac and scrub it out with bleach and spray nine.
Make sure there are no fuel leaks. Diesel odors get into everything aboard if there's a leak. If you have a gas engine, well you know the dangers of a gas leak. Solar vents help a lot with odors. Read the Head Mistress section of this site for advice on dealing with head odors.
If there's a carpet lift it up and look for mildew on the underside. If there is you can replace it with a carpet remnant (cheap) using the old carpet as a pattern.
It's also hard to get used to living with so little storage space. We're on our third summer with our boat and I feel like we've finally got our boat organized so there's little or no clutter. Check out
Right Track storage bags. We've had good luck using them to add more storage.
Battery operated LED lights are a great way to add task lighting. We have them in lockers and use a large one from BB&B for galley lighting.
Living aboard I'd also think about investing in a set of doors. They're not cheap but it's a LOT easier than lifting hatch boards in and out all the time.
Zarcor makes a really nice set or you may be able to make a set yourself.
Canvas repairs are expensive.
Sailrite is a great source for canvas projects and boat parts if you want to tackle them yourself. If not talk to other liveaboards, a lot of folks do canvas work for side money, just make sure they do good work.
Finally you have a Catalina so check out CatalinaDirect.com and Catalina30.org. There are more Catalinas than any other boat brand, that means there are a lot of things made just for Catalinas.
Best of luck,
Jim