Gerry,
The units are different. I can't speak for longevity's unit or its capabilities or their claims. I do know theirs doesn't have the lift tig function.
There isn't any thing to a stick welder manual or basic tig for that matter. When it is completed, nothing in a manual will teach you how to weld...only practice will.
As you have done any specific questions can be addressed here.
As for your question about polarity...Sure, its not problem... Its the same as any other welder with dinse connectors...just swap the cables...But the BIG question is why would you? Keep stick with the electrode holder in the positive, and TIG with the torch in the negative.
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