I would agree that five weeks to change a part that would take me (an amateur) 40 minutes to change, simply is not cricket. I would have asked about the possibility of a loaner at the time of the malfunction - and I would have been polite about it.
If it was a store that I, or any of my colleagues ran, then we'd ''sort out the customer first'' then worry about who pays for it later. If Giant didn't like it, we wouldn't sell their gear any more. If anyone in the future asked why, we'd tell them the truth. Our company have done this sort of thing several times in the past. (Yes, I do work in retail.) Manufacturers get the message pretty quickly when their sales team come round looking for orders and get only "No thanks. Nice product, rubbish customer service. We're not having your firm ruin our reputation."