Yes, you've learned the hard way! I did the same thing: I had been a member of my local club for some time and was hardly getting any instructor time, so I took matters into my own hands. I reverted to a 3 channel Ripmax Zephyr and flew that at the club on my own even though I hadn't soloed. The other club members commented that I could fly but couldn't be certified solo unless I flew a 'proper' trainer with an instructor. I lost my Superstar 60 to the 'balsa tree' on approach because the instructor was so confident in me he wasn't even looking. I had placed the plane further out as it was larger than the Zephyr I had been flying. After fixing it up I landed it in another tree 50ft a couple of weeks later when I decided to go to the field early and fly on my own. I've learned that the only way to be sure is to ensure that there is plenty of blue stuff between your plane and the green stuff on the downwind leg.

For replacement, the easiest solution would be to get a replacement Nexstar airframe, but depends on a couple of things:
1. Did you like the plane enough to want to continue with it?
2. Do the fuse and wings kits give you a complete airframe, or can you unbolt the tail easily? Considereing the price, you'll want an as good as new airframe when you're done....

You were asking about a MkIII Hobbico. The only MkIII that I know of is the Hobbistar which is a 60 sized plane. From my experience I wouldn't recommend this one.
If you wnat to start afresh with a new plane using your existing radio and engine I'd recommend the SIG LT-40.