just bought a 2016 shadow cruiser. had a few very old campers and pop up in the past. so how big of a deal is a surge protector? and if you use one what do you use?

Surge suppressors are a good idea, we have this one... for now:

https://www.campingworld.com/southwire-portable-surge-guard-protector-30-amp-73993.html?cgid=power-protection

But, what else is just as damaging, is brownouts, or when the frequency varies too far from 60Hz.  In that case, something like this is a lot better option:

https://www.campingworld.com/progressive-industries-ems-pt30x-30-amp-ems-with-surge-protection-18l-102484.html?cgid=power-protection

Eventually, I'd like to install an EMS unit inside our camper, and have a monitor display mounted on the wall.  Something along the lines of this:

https://www.progressiveindustries.net/ems-hw30c

Some people don't run them, to each their own.  Cheaper to replace one of those than it is to replace appliances or your converter, and easier, too.

Most people use them because they are cheap insurance against shore power issues. No reason not to use one truthfully.

Progressive Industries RV Surge Protector 50 Amp, Portable with Cover, SSP-50XL https://a.co/d/cixnZXR

We always ran "unprotected."

Stayed everywhere from Ft. Wilderness, down to some hole-in-the-wall type places.  Never had any issues.  Appliances, TVs, laptops, tablets, phones - can't recall a single issue over 12 years of camping.

99% of voltage problems at the RV park
256 spaces and 130 at a different location is the surge suppressor,
Some are great, if you get the better ones
I Tell people I am gonna hurt their feelings when they complain about the power and all I do is disconnect they’re junk surge suppressor (TVSS is the proper term)

I prefer hardwired EMS surge protectors. Can’t be left behind or stolen. Last December the plug on my 50 amp shore cord shorted sending 240 volts up both legs. EMS saved my ass.

I rarely stay anywhere with shore power, we're primarily boondocking when we camp, but with a trip to Cali in the near future, I figured I better get a surge protoector. Ended up with this one from Camping World.

Camping World Surge Protector