My suggestion would be listen to Tom and follow his guidance. Good wheels would be the best investment in your case. The tougher part will be finding the extra large frame because of your height. Good luck!!!! and of course have fun at the same time.
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2007 Jamis Ventura Comp
2006 Jamis Explorer 2.0
2000 Specialized Hardrock (bought used)
Swim, Bike, Run and sounds like fun