2-3 hours for both sides for a first timer may be a bit optimistic, though it sounds like you may have access to good tools (perhaps just the right spring compressor?) and help, so maybe....
You can certainly do just one side at a time, so long as you mark the position of the excentric bolts very carefully to preserve your alignment.
Best to get a real alignment after the other side is completed.
Best of luck.
1986 300E 5-Speed 240k mi.