Poorly trained for what? What exactly is important in a wizards training?
Knowledge, particularly knowledge of spells and potions as well as what is effective vs ineffective against various supernatural beings. And in that regard, Harry had one of the best teachers of all.
Bob taught him the spells to enforce his duster, the spells he uses in investigation, ALL the potions he's ever used, every bit of supernatural knowledge and lore, etc. etc. And everything Harry ever learned from Bob was for a practical purpose in one form or another, which means he learned it well and it stuck with him because he had uses for each and every bit of knowledge.
It's true that by the standards of other Wizards Harry is very lacking in overall wizardly knowledge. But he has cherry-picked the most useful pieces and made them his own thanks to an extremely helpful skull. He is NOT poorly trained as a wizard any more.
I doubt that Lea could heal him anyway, what she did for Susan was temporary if I remember correctly because Harry got all excited when she did it, and asked her about it.
Lea said that she put their Hungers to sleep, in response to his question. she didn't explain how she did so or what her magic targeted in order to accomplish that. Harry WOULD have to offer something in return for the knowledge, but it would be a better starting point than his current start of "zippedy doo da".