Assuming, I've never imported my pre-sale wallet from the initial ethereum crowd fund, could I simultaneously send the the contents of my wallet to an ETH address and an ETC address? I'd like to sell the ETC from the wallet but don't want to risk losing ETH.
As long as you send your ETH to an ETH address which you have the private keys to, you are not losing your ETC. ETH addresses are also valid ETC addresses!
After importing your ETH from the presale wallet, it will (should?) also import your ETC from the presale wallet in the very same transaction on the Etherem Classic chain. You should have both your ETH and ETC on the same address. You can carefully check this by running two geth or parity instances on each chain, e.g.:
parity --chain homestead --port 30303 --db-path ~/.parity # ETH parity --chain classic --port 30304 --db-path ~/.parity-classic # ETC
geth --support-dao-fork --port 30303 --datadir ~/.ethereum # ETH geth --oppose-dao-fork --port 30304 --datadir ~/.ethereum-classic # ETC
After importing and holding both your ETC and ETH on your local account, continue with splitting them carefully by following this excellent guide.