I'm glad you enjoyed your maiden voyage sea trial with the 'new to you' Sunny, welcome to the club.
A few things I try to pass on to people who have trouble backing in...
try to always start you back up when the trailer and tow vehicle are lined up straight. It's much easier to make small steering corrections from this point and return to straight if you get really 'out of whack.'
with one hand at 6:00 on the wheel, steering from that position to the left will take your trailer to the left and vice versa.
if you get too far 'out' backing up and are starting to jackknife the trailer/vehicle, pull back out and straighten up and try again, don't try to recover the alignment by continuing to back up.
use a spotter behind the camper to direct the driver around possible hazards with previewed hand signals you both agree upon, especially stop!
when you're in a tight area, don't be afraid to get out and actually look at your trailer placement and your side to side level indicators.(if equipped... if not I'd get a couple for your 'front to back' level and 'side to side' level) A hasty 'drop' and you'll find yourself with days of inconvenience of a non level camper. It's worth the comfort factor to get it done right on the 1st drop rather than hooking up on day 2 and moving the unit a few inches/feet to find the right spot.
Hope that helps a little to getting her backed in for some camping relaxation.