If you look I said if you buy new/used from a dealer you will/maybe charged taxes. If you purchase from an individual you do not pay taxes and I mean SALES taxes. there are no taxes generally to license per se but there are registration fees for license plates and sometimes there are velorum taxes, but it will depend your legal residence. I only paid to have the rig registered no taxes but also as I said the registration is generally based on msrp.
An extended warranty is basic insurance, you are trying to cya if something goes wrong. a lot of the warranty ones referred to above are the fly by nite ones from the dealers where they make profit on new used vehicles. I dont know about the GS one but they are a national firm who will not take a chance to sell a product that doesn't work as advertised.