A one year health guarantee is great Not many breeders will offer that long. I doubt it will cover any reimbursement for vet fees, most people i know have pet insurance, well worth getting if it available where you are.
If you are going to be away at times & if it;s only a couple of times a year i dont see any problems as long as you have someone who can care for your bird, in your own home is best, or someone your bird will be use to.
When you say physical ailments, do you mean physical signs of illness ? birds are great at covering up illness, the tell tale signs would be showing signs of being lethargic ,loss of appetite, any distinct changes in the poop, sitting fluffed up continuously & resting on two feet instead of one,
once you own a grey you pretty much know what is normal for your bird, anything that is out of character for your bird you will pick up on.