How to correctly import old wallet file, with possibly a small issue

I have an old wallet file that I want to make sure is ok and have a few questions on how to best proceed.

I just got back into bitcoin and the original file resides on an old pc. I have several backups of this wallet. I was kind of an idiot and started up the client and downloaded the blockchain, then tried to make a 5BTC transaction to another wallet of mine. However, this transfer never went through. On the sender client it said in thestatus column:" 0\unconfirmed: network problems?". This was at the exact same time as the blockchain split a few weeks back. I shut the client off after a while and it has not connected since. Checking blockchain.info shows nothing on the respective addresses.

So, what is the best way to restore my wallet? Should I just use one of the backups from before this happened, or will this cause any problems?

I am also wondering if it is safe to just store the wallet.dat file indefinitely or does it need to be updated in some way at whatever interval?

I would really appreciate some help in this matter as though I have played around with bitcoin for a few years I still don't know much about the technical side of it.