What do I do if my 1998 Toyota Corolla hits the curb after sliding in the ice and snow and it makes a loud rattling noise?

The rattle (noticed at times under hard acceleration) is the cause of gas shock on the upper part of the engine loosing charge, in-turn causing the engine mounts extra stress and thus metal vibrating/rattling together.
The knocking (over bumps, etc. if you have noted that) is caused by worn bushings, most likely worn sway bar end links (you will see the links looking at the undercarriage, on both sides, they are a little steel "bars" with threaded ends on a 90 deg angle held by bushings e.g. example of front sway bar links ).
I noticed these noises coming on (at various times) at about ~140,000km or ~67,000mi and drove the car as it was until ~300,000km when i sold it (as is). Annoying noises.... yes... did I turn up the radio and carry on driving this car, not "fixing" anything (and I mean not a single $ spent on it aside from maintenance) and then sell the car... yes. The choice is yours.

How much would what cost?

You said you MAY HAVE loose panels

If you haven't looked over your
own car or had some check it out,
how would we know anything,were on the
internet.

this may mean your catalytic converter is broken and the rattle from the exhaust hanger that could have broke when the catalytic converter was struck by hitting a speed bump too hard or a curb.

When both wheels are in the air it is normal that one wheel will not turn when put in gear.

There is nothing wrong with the axle or the transmission.

sounds like you may have hit something under the snow I suggest you not drive it till you get it checked out

It amazes me that they didn't at least address the rattling noise, seeing how they probably caused it. If it is just a belt, that's an easy fix. Did you stop at another shop & ask for a quick diagnosis?
Could be something as simple as a heat shield , or something. Doesn't hurt to have a second opinion, and shouldn't cost anything, or very little, then go back & tell them what the diagnosis was.

it provably unbalance blower fan or improper installation blower assy. try to remount it.

Sounds like you got a bad stater or the engine is locked up try to turn the crankshaft if it turn then tap the starter with a hammer while someone else turns the key to the start position if it then starts you have a bad starter.

timing chain tensioners are commen on the 1zzfe. the tensioner is about $50 and the labour another .5 hours.

The hit may Cause a serious damage to the car legate-it can be a lot of thing u have provide more info