If your battery is dead, you will not be able to shift it out of park (unless you read the section in your owners manual about that), and is the cause of the rapid clicking.

Now just why would you be concerned your engine is "shot"/"blown"? Did you continue to drive it after the rock incident?

 

I pulled off once it happened but was in a dangerous spot so I let it cool down and drove on a half mile to a safer spot.

 

Ok..... so I'll ask again - Now just why would you be concerned your engine is "shot"/"blown"?

 

Neither party has insurance?

A rock that big probably fell off the trailer not kicked up.

If the battery is good the engine should, at least turn over, regardless of the state of the radiator.
Perhaps one of the grounds was broken.

Find a GOOD mechanic. There is nothing special about HHR brakes or mechanical systems. You should replace things in pairs.

If one wheel is straight and the other is toe out you have a total toe out. The steering wheel should be centered after an alignment, you may start getting Traction control warnings

 

I don't have full coverage and the big rig the rock came off of didn't stop.
Well I'm not sure how easy/hard it is to blow a head gasket because I've never driven an overheating car. I guess I'm being hypersensitive.
I'm waiting on new radiator and fan to arrive. Any common mistakes or easily missed details I should know about?

 

Luckily, replacing the radiator and fan is a pretty easy job, just take your time with it and be careful will disassembling and reassembling all the pieces. Also make sure you take heed when refilling the cooling system as the HHR likes to keep air in the system. If you are not comfortable completion the repair, them have it professionally done. But be warned, they will kind of screw you over based on the "book hours" that the job says are required. I damaged my fan by mistake, and I had the old one out and new one in and running less in less than 45 minutes; and that was the first time touching any fan of any sort, and all I did was watch a Youtube tutorial.
Of course for the radiator you will dig a bit deeper but due to the design of the HHR its really easy! If the radiator was damaged I would inspect and replace the condensor as well. All parts can be found very cheap on AMAZON, I got my fan by TYC for 53 bucks!
As you go, post up questions as you have them, DONT post after something is already messed up. Just ask! We dont bite! (hard)

 

However, replacing the A/C condenser is a job better left to a pro. It can be dangerous

 

Yes, system must be completely depressurized before touching it. Correct?

 

Yes. But if the OP has a hole in the condenser from that rock, then I'm sure that the magic gas has leaked out and there's no pressure on the system.

Seriously though. He'll need a vacuum pump at the very least to tackle that repair. Been there done that, back in my mechanic days.

 

This really makes me want to consider installing a lower grille!