I have actually thought about going into small engine repair myself. I can fix almost anything, but have no training..... so I didn't want to get in over my head if I got into that business without training. You have the training and actual hands on experience!
If I was in your shoes, I would do the engine repair! As soon as you are able, you could buy or lease a shop and then you could be charging the $65.00/hr! And before you know it, you could be buying and selling used mowers and a couple of years later, operate a large equipment dealership! That would be my plan anway.... Good luck!