How to setup a SQL cluster using MS SQL?

"...is this something that is extremely difficult..."
No.

"...I should bring in a team that is familiar with this process?"
This depends on your comfort level, but the process isn't difficult:
Build the machines.
Add Microsoft Failover Cluster Services
Install SQL Server
Optionally establish SQL AlwaysOn High Availability

"Any tips beyond what I am reading"
Maybe read up on Failover Clustering and AlwaysOn HA

"What versions of MS SQL support clustering?"
All the modern ones.  The last several versions of SQL Server are "cluster aware" <- maybe read up on what that means.

I would assume you would need at least two SQL servers to do this? What does clustering get you that SQL replication does not?

"I would assume you would need at least two SQL servers to do this? "
Yes, at least two physical or virtual servers.

"What does clustering get you that SQL replication does not?"
A Failover Cluster can fail over when one node becomes unavailable.   In other words, you're not just duplicating the databases, but creating one, large cluster of servers.  You only ever talk to one real server at a time, but you don't know (or care, usually) which one.  If that server goes down for some reason, Failover Clustering simply grabs another SQL server and puts it in charge.  Downtime is usually minimal and the transition may go completely unnoticed.

In this case, we are talking about security for an airport to keep the planes flying and commerce moving. You both have given excellent advice and it is very much appreciated. I will add that the request for clustering came from their IT consultant who is not a database person. I will speak directly with the client next week and find out their true plans.

"to keep the planes flying and commerce moving"
If the SQL Server is critical to this mission, you're completely justified in failover clustering it, depending on your threshold of pain.  If you can afford some downtime and/or lost data, just having reliable backups you can reliably restore from may be an adequate solution.

Thanks for your tips.