No, you don't need to stick with Truvativ, but you will need to be sure it is milled for Campy. In other words, don't get a Shimano crank. Also don't get Fulcrum. Even though it's made by Campy, it's milled for Shimano. Get Truvativ, Campy, etc.

Campy rear derailleurs can take larger cogs than Shimano or SRAM, so the 29 would work.

Something that I don't think has been said about the option you were considering is that with a 53-42-30 triple, you might start having trouble figuring out when you want to be in the middle and small ring. The jump from 42-30 is big. The 42 is also going to be harder than your current small ring (39). So, there could be a lot of situations where you'd feel like the 30 is too easy, but the 42 is way too hard.

Just changing your cassette will make a big difference. A 23 is a pretty small easy gear there. Then I also agree that it will be a lot cheaper and easier to go to a compact crank. You might want to do one or the other at first. I'm not sure how badly you're struggling with your current setup. Putting on a 13-29 with a compact will make you lose a lot on the top end (like when you're going downhill), and perhaps you don't need a 34 ring with a 29 cog as your easy gear. There will also be a wider spread in the middle, which can get annoying on the flat. If you go compact, do that with your current cassette first. Then see if maybe you'd want a 12-25, 12-26, 12-27, 12-28, 13-29, etc.