@dnimigon
Justin and jssailem give good advice. The problem is when something does break it could be a nightmare to find and fix.
As jsssailem said, especially about reading the articles at the marinehowto.com site. MS goes into a lot of detail but his advice on making good connections is invaluable. He has articles on marking wires, making good crimp connections and what tools to buy, battery cable connections, etc.
Then read through his forum "Musings with Maine Sail" here on sailboatowners.com You find a lot of good ideas by reading every thread that looks like it has to do with electrical.
I don't blame you for wanting to neaten up the wiring, especially when I see wire nuts being used.
If you want a new panel check out
www.blueseasystems.com. Another panel maker is Paneltronics. Blue Sea is pricey but they make nice stuff.
I just acquired a 93 C30 and here is what I am doing or going to do on my boat.
First thing I did before doing any work in the panel is identify any and all AC 110 wiring.
You need to fully understand the AC wiring as a live 110v wire may be the same color as a 12v ground. Not knowing the difference can get you killed.
If this is beyond your capability, then stop and get someone who knows how to do it.
I suspect the breakers on the left of the panel are your 110v service breakers.
You need to cover them with a protective cover of some sort before you start so there is no chance that you plug into shore power and accidentally lean on one of those live wires while working on the panel.
I got mine from Catalina Direct. Les from these forums suggested an upside down Tupperware container. Much cheaper.
I will be replacing the panel in the future so I plan on cleaning things up a bit by up by very carefully identifying the wires with numbers and making a list of all 12v devices on the boat.
I'll be getting a pack of number tags for wiring, available from any hardware or big box home store like Lowes or Home Depot. Also got a bag of 6" zip ties. I identify each wire by what switch it is attached to. Tag it with a number and make a list. Then try to bundle wires together based on use using the zip ties. When I come to a wire nut or some other non marine connection I'll use heat shrink butt connectors of the appropriate size to replace the wire nut.
When I come to wires not connected or running off somewhere I can't trace, I'll mark them as such so I can follow up on them at a later time. Maybe bundle them together as well. Old boats have a lot of abandoned wiring.
Identifying wires, making neat bundles and eliminating bad connections will be done on non sailing days. When I'm ready for a new panel I will be far ahead of the game. I know I will go with a Blue Sea panel.
Of course I have many other projects of higher priority but for those days I can't move forward on those other projects or go sailing I'll work on identifying the panel wiring. Then some winter I will change out the panel.