1 day, Id hire my own car & driver. Make sure to see the Chu Chi tunnels and the other 1/2 of the day you can do on your own especially from the IC, walk by and step into the Post Office a couple of mins from the IC, then the church across from it then to the Palace a few mins walk and tour it, if still time The War Museum and just take in the French colonial buildings as you walk the Opera house is nice as the hotels surrounding it

Still have some time Ben Thanh mkt (there are better but its close by) and if they finished redoing the outside The Peoples Committee

Everything but War Museum and Ben Thanh mkt are all in the area near the IC. Yet they are also walkable.

The main sights can be seen in 1/2 a day thats why I suggested hitting the tunnels.