Single-handing a Catalina 310 while sailing is easy, even if the first time is nerve-racking. I did it for the first time within weeks of buying mine and it was my first sailboat. Close quarters, on the other hand, is harder but still just a matter of practice. Watch videos, read books and maybe even take an in-person class (my wife and I took a weekend-long class in the Chesapeake at the Maryland School of Sailing and Seamanship with two of our adult children and it was a game-changer). You could also hire an experienced skipper for a day to practice with you. Practice in an uncrowded area by approaching a buoy under power from different wind/current directions to get a feel for momentum, speed, prop-walk, etc. and practice some more. Just like driving in snow, the single most important thing is to take everything as slowly as you can. Good luck!