I think that breaks down to a few questions, both difficult to answer, so here's my thoughts:

1) Are there going to be issues relating to replay attacks?
Possibly, which is why people have been pushing 2x to implement replay protection (it's not possible to do this on the current version without making your own fork). Core have attempted to mitigate this by rejecting BTC1 nodes in the latest release of Bitcoin Core. But now we have the possibility of BTC1 nodes pretending to be something else so they will be recognised by the Core nodes (which makes little sense as far as I am concerned). Replay protection may be as simple as waiting for the fork to happen, then transacting with a specific node type you want your transaction on (some light wallets allow you to effectively "pin" trusted nodes), if the network is already segmented then your transaction shouldn't be broadcast on both.
Another option is to get some freshly minted bitcoin post fork (either one will do), move your coins and include this post fork bitcoin, this will be rejected as invalid on the other chain (those coins don't exist there). You can then safely move the coins on the other chain as the first chain would have those coins as spent (and therefore the transaction would be rejected also).
As to "destroying value", maybe, for some people it could be an issue, however any coins sent on the wrong fork would still be recoverable by the receiving party as the address format hasn't changed, so they could just claim the coins on that fork. It's a massive hassle though, more confusing than technical issues however.

2) How will the fork affect price?
Hard to say, some expect it to increase the price (as it appears to have done in the run up to the fork) as people will be getting 2 potential tokens, however once it's live, one of the forks may drop in value, with the money migrating to the other fork. It's safe to expect some volatility, with one side emerging on top, how long this takes, who knows? As long as one side doesn't have all the hashing power, difficulty will adjust (will likely be slow on the Core chain as most big miners support NYA) and the coin will become usable again. One of the chains will be slow though, as there's no "EDA" as implemented for BCH.