Using Electrum within TrueCrypt container

Hi guys.

I want to use Electrum within TrueCrypt in an offline mode instead of leaving the wallet on an online computer_ "run electrum, import the key, pay someone, then log off and wipe the electrum.dat file".

But I already have an Electrum wallet with a few btc. I'm not a techie and reading things about wallets making me kind of paralysed for doing anything. It's like in case I did something wrong with Electrum installation or existing wallet, I will lose all the btc in it. (Information on Electrum website is minimal).

My question is that if I now open TrueCrypt container then install Electrum in it, does Electrum allow 2 wallets on the same computer? or Will it create a new wallet in default folder, potentially overwrite existing wallet? or collision between wallets?

Maybe I should backup the .dat file before install Electrum. But it still confused me. Is it safe just to copy the .dat file to a safe folder and restore it later on? Alternatively Electrum provides a backup function. But what's the point of backup function while one can restore the wallet using the seed only?

I guess these are simple questions, but bear with me please. I really need to get my head around it. Thanks.