Hard drive errors but SMART is passing
Would now be a good time to go ahead and replace my hard drive or am I
  good to wait for a little while?


The answer comes down to your answer to the question "What's your data and time worth?"

The bottom line is that the rotational (mechanical) drive that services your data is at it's end of its useful life. It could go on for another 6 months or last just another 6 hours.  It's impossible to know for sure.  What we do know is that it is starting to fail.

The best course of action (in order of priority) would be the following:


Make a (Time Machine) backup
Upgrade to an SSD or new HDD
Migrate your data from your old drive


I go into detail about the above steps in a similar post. 

It's best to do it when you can schedule your down time as opposed to dealing with a forced down time because the drive invariably failed (and usually at the most inopportune moment).