Upgrading from 15" wheels to 16" wheels??

I recently purchased a 2009 4x2 2.7L access cab. I have put a few things on it, such as a Leer cap, Toyota wind deflector, front mudflaps, vent shades and stainless steel exhaust tip. I think my truck looks pretty good.

As soon as I bought my truck I upgraded from the OEM Dunlop P215 70R15 AT 20's to Nokian Vativa P225 70R15's and I haven't looked back.

However there is one thing that bothered me about my truck and that was those ugly 15" Toyota steel wheels!

So I recently decided to go shopping for some nice mag wheels for my truck and found that it is hard as heck to find nice black 15" mags. After a while at my local Kal-Tire I decided to upgrade to 16" wheels and a 16" Nokian P225 7R16's.

Now I did some research and realize that my speedo will be slightly off...65mph for instance will actually be 67.73mph.

So here is my question. Besides the speed are there any negative effects I should be aware of? Can, or should I get my speedo recalibrated? If so, where can I get it done? (The Toyota dealership had no idea!) And how do I calculate my mileage? If for instance I get 500km out a tank...how do I know how far I have actually gone?

Thanks,

Derek