We just bought a new to us Catalina 36 this July, and so far we have done some upgrades that were recommended by the survey and some others that we wanted to do just for our own peace of mind.
1. Replaced all freshwater plumbing with pex
2. added an accumulator tank to the freshwater system.
3. added a gps to the pedestal
4. upgraded the stereo, (couldn't stand not being able to play my buffet cd's or the wife's ipod)
5. replaced the nicro solar vent with a day/night solar vent that actually works.
6. re plumbed the 2 electric bilge pumps
7. have started replacing interior lights with LED's
8. added red LED courtesy lighting
For the winter I plan to pull most all the doors, and drawers etc, and refinish them at home. I also have replacements for most of my running rigging at home just waiting for winter to splice it and such. Also hope to upgrade the electrical panel and the battery/charging system in the spring.
And I am sure that I will run across 3x more projects as I work through this already long list. I do like working on the boat, because even if it doesn't go well at least I accomplished it, or didn't myself. I didn't have to have supervisor authorization, committee meetings to decide how to attempt it, or process review meetings while in the middle of it.
It's the little things in life. Cheers