How do you know what audio system you have?

[Cunningr]

I just did a full blown upgrade.
Hertz 3 way components, pioneer PRS 80 head unit, Alpine pdx 9 amp.

Used the metra plug from crutchfield had them do the prewire for $20 head unit plug and play. Dash speakers used CAI speaker kits, bit pricey, but makes installation a breeze.

For door speakers they will hold 5.25 direct bolt in, but they are subs so unless you change amp will only get low freqs. I put 6.6” in by buying and modifying speaker box from ebay. Truth be told change hu, and dash speakers will improve sound by tons. A single din fits so you can go back original if you sell.