dash gauges and lights

1988 Nautique 2001
I know the gauge of wiring used was a little small, that being the reason for gauges changing what they read when running lights are on.
I'm going to have to rewire my cluster. Looks like someone, that had no idea what they were doing already attempted this.
So I have a few questions.
1) what gauge of wire recommended to fix the starving issue? 12, 14, 16, ?
2) Would I be devaluing this 1988 Nautique if I went with all digital gauges?
3) What push buttons have been found to be the best replacement?

All gauges work, I removed the clock and installed a through hull depth finder. It is digital, but matches the dash very well. It also works at all speeds. I like it :)

Thanks everyone,

Alan,
I recommend using marine rated wire. It's tinned to prevent corrosion. When it comes to crimp on connections, I suggest the heat shrink adhesive lined type.