My pressure tank just blew

Yay. The big blue pressure tank on my well had spring a leak.

I've thrown the breaker for the hot water and the pump, and collected what water I can.

Big box stores have replacements locally, is there anything I need to know?

It looks like a 1"rubber line straight from the pump and that's it? Do I have to pre pressurize or do anything crazy to replace it?

If it's not pre-pressurized you may need to pump up the bladder. There will be a schraeder valve on it and a bicycle tire pump is recommended over using your compressor to inflate it, prob around 40 psi or so. You may need to re-prime your well once it's installed depending on if your pump is a pusher or a puller.

I replaced mine years ago with a Home Depot one.  It's not difficult, but mine was all hard-piped with copper, not rubber, so I had to do some soldering.  I want to say it was pre-pressurized, but I'm not 100% sure.

home depot has then pre pressured, and way cheaper than everyone else. It's scary this looks so easy.something bad will happen.

Priming the pump again could be tricky, I'll probably have to do a water run. 

Any neighbors close by that you can join some garden hoses together to reach your system?

Water is cheaper than hose haha.

Turns out, the cast iron elbow on the bottom of the table rusted through. The tank itself was fine. Still for all it cost, replacing the tank and running a fresh line with pex

Wow. I'm actually scared something is going to break. Old plumbing isn't supposed to go that smoothly. 

Granted 3 trips to Lowes depot for fittings because even with 2 of us working on it, we missed things, but simple. Holy crap are pex tools expensive, and shark bite connectors, but those shark bites are worth it. 

So what should I do with my new 20 gallon tank? It feels too light to be a good smoker or fire box, I still haven't finished my other foundry, there's gotta be something fun to do. 

Double check where your pre-charged tank is filled and compare it to where your pump is set.  Many of them come at 40 psi which is fine for most 20-35 psi settings.  I had my house set to more like 30-50 psi so I added a bit of air to my tank.  Conversely, you can also change your pump cutoffs to match the pressure in the tank.

The 20 gallon tank makes a great planter cut in half.  It could be a fantastic kerosene/diesel can.  Maybe a bouy to mark a shallow spot in a lake.

Or it would make a lovely grill/smoker but like you said it just may not last long being so thin.

Custom muffler for a truck?

rainwater collection unit?

You could do what I did and turn it into a fire pit.  Mine was a huge 80-gallon commercial unit, but a couple hours with a plasma torch gave me this:

If you have the type where the pump mounts on top of the tank, you will have a harder time finding a replacement.  Tractor Supply has those style tanks with the bracket on top.  Decent tanks, decent price.  The recharged pressure in the tank needs to be 2psi lower than the cut in pressure on the switch.  Use a tire gauge and check the pressure before you fill it with water.  Throw away the old gauge and install a new one.  New pressure gauges are less than $10 and you need to know exactly what the cut in pressure is.  If you have too much air pressure, the air bladder will push all of the water out of the tank and then the switch may or may not see enough of a drop in pressure to kick on.  You can get away with more than a 2psi negative difference, but every psi lower than that means your draw down cycle(gallons of water used between cut off and cut in) will decrease.  Electric pumps/motors don't like to short cycle.  They like to kick on, run as long as possible, and then kick off.  Shorter draw downs will decrease the life of your pump.  Thats why the larger the storage tank, the better.  If you have any more questions or have questions that can better be answered with pictures, feel free to email me.  I can talk you through it.