Are the $18,000 401k 2017 limit and the $5,500 IRA limit mutually exclusive for a combined limit of $23,500 (under 49)?
Yes, but the amount that you can deduct from a traditional IRA depends on your gross income and marital status - See publication 590-A for details. Also note that the limit applies to your combined traditional and Roth IRA contributions (meaning you can't contribute $5,500 to both; just a total of $5,500 between the two).
I'm also assuming employee match $ count towards these limits - is this correct
No - the limit for combined contributions between you and your employer is $54,000 in 2017. So if you contribute $18,000 your employer can only contribute $36,000.