New guy with questions

Let me start off by saying I'm new to the forum, I'm also going to be new to the diesel world. I am thinking about buying a 2014 6.7l f250 Crew cab. It does have some mods done to it and that is what I have questions about. It has a 6" rough country lift with 37" tires. Is this set up going to cause issues to the stock 3.55 gears or to the tranny? It does have an intake, exhaust and mini tuner, soon thinking that should help with the power loss, am I correct by thinking that? I have also attached a link to the truck, if you don't mind taking a look at it and telling me if you think the price is fair or not. Thanks for any and all help!

http://www.myindyford.com/used-Zion...RW-Super+Duty+F+250+SRW+XLT-1FT7W2BT2EEA20308