Simply updating the radios is relatively simple for a good shop, depends on what you're wanting and willing to spend. A new 430 and a couple other new radios will cost around $20k installed. We paid around $7000 for a used KY97 and KNS80 plus new CDI plus used KR86 and plus dual avionics masters and some other minor work, installed. Understand those were all used, refurbed radios, not new.
Remanufacturing the panel to move the gauges around can be more complicated and would require a field approval I believe. You've got to change the plumbing and wiring, look at lighting etc. I know some guys have spent $40-$50K on their Cessna panels. Most all will tell you it's far cheaper to buy an airplane with radios and panel you can live with. I've been dreaming of a new, powder-coated and silk-screened metal panel for the Cessna, along with a refurb of the electrical bus, breakers and panel lighting, and that's around $7K installed as well, with a pre-engineered kit that's already been field approved numerous times. You might double that figure and add 1-2 months for a one-off Commanche panel.
All the above might well be worth the money and effort if you plan on keeping the airplane for 10 or more years, otherwise, it's money you'll never get back. Consider a newer Arrow with modern panel.