First things first. You should not have to add accessory anything to get a new (this is a 2010 remember) to drive down the road safely. If you need to add helper springs, levelers or anything to have it drive relatively straight, those are excuses to cover up something wrong. Either it needs adjustments (repair) or is defective.
If it is less than a year old, then the Winnebago warranty comes into play in a lot of cases. The trick is to accurately identify the symptoms. Stay away from terms that mean different things to different people.
Take your rig for example. Get it on a straight smooth level road. Drive it at different speeds up to freeway legal and at each speed note what happens. If it doesn't run straight without constant correction just to keep it on the road for short distances, note which way it drifts and how fast. Something like "within approximately xx feet or xx seconds it pulls to the right or left". Another example: at xx mph the steering wheel shakes left to right or up and down xx inches. It isn't that difficult to do but that way you are putting numbers on something and quantifying the symptom.
Full documenting specifics is essential.
As others have said, check to see if it has been involved in an accident. Call Winnebago and ask them for a replacement parts and prior service history for the specific reason of determining if it was involved in an undisclosed accident. There is recourse available to you if it was in an accident and not disclosed.
As for leaving it at the dealer for such a long time. You have a right to know the estimated time for repairs. Ask the question directly and don't take "waiting on parts" as an answer. Any parts you could possibly need are available within 2 weeks. Longer than that and you are being held hostage so to speak.
Get all your existing warranties together and read them. Make sure you know what is and is not covered. The various manufacturers of components will all provide you with written warranty disclosures. Don't reply on what you read on their websites, those are usually only summaries.
If you are paying for repairs, you do not need to go back to the selling dealer, especially if they aren't getting things done. Go elsewhere.
Always pay for a diagnosis. Here is the reason. When you pay for diagnosis, the dealer must be then able to fix the problem according to the specifics of the diagnosis. If they come back later and then claim it was something else, then you are not liable to pay for the work done because of a faulty diagnosis. This is not some art, it is a science and the repair of mechanical things can be diagnosed. Many dealers will just want to swap parts until something works. That is called guessing and no one should pay for that. Most often, the parts swap will not fix the actual cause, it will address a symptom only. Worthless.
Use only a credit card when you pay for service. If it isn't right you have recourse with your credit card company. With good documentation, you will prevail.
I think that if you very clearly and accurately (with facts- numbers and so on) explain everything, Winnebago should be able to provide quite a bit of assistance.
You don't need to get nasty nor do you need to be run over and get shafted because someone who is liable for what was sold to you doesn't want to lift their finger to take care of things