Could someone do a step by step on how I would
store sxc in a offline cold storage wallet, and then send them to a marketplace when need be.
Also when stored offline can anything happen where the coins can be accessed by a hacker if they do not know the private keys, or say for example the chain goes wrong or gets corrupted for example.
You can do the following:
1. Create a cold storage wallet
Option A would be using a Ledger would be the easiest but since there is no Ledger support for SXC you can do option B or C. Option B is to use a paper wallet generator to create a keypair. I am nto aware of a paper wallet generator for SXC so you can follow option C. The last option would be to prepare a new PC from scratch without connecting to the Internet. Copy the wallet installer from USB to the new PC. Install SXC wallet onto the new PC. You dont need to sync the chain. Create a bunch of new addresses in the wallet. Do a "dumpwallet dumpt.txt" and write down all the key pairs on a paper or copy dump.txt file to a USB. Erase the PC by overwriting all the sectors on the HDD with a tool like Active Killdisk or Wipedrive.
2. Sending coins to a cold wallet
Send coins from your hot wallet to one of the public addresses from the key pairs you wrote down. Confirm in the blockexplorer that the coins are in the public address.
3. When you need to send coins
Import into your hot wallet the private key corresponding to the public key where you sent the coins to. The coins will now be in your hot wallet. Send the coins to exchange for example. Send remaining coins from your hot wallet back to the second public key of the key pairs you wrote down in step 1. Rince and repeat. When your key pairs run out or when you insert the USB to your PC with the hot wallet, repeat step 1 to get a new set of key pairs.
When stored offline in a cold wallet your coins are safe, unless you made an error writing down the key pairs, or when you insert a USB with the key pairs into a PC connected to the Internet then consider your key pairs less safe. Your coins in a cold wallet will be safe even if the chain splits as long as the coins were sent to the public key while on the correct chain. A hot wallet will import the coins from the key pair of a cold wallet when you resync a hot wallet to correct your chain as long as the coins in the key pair was sent there while on the correct chain.