Rim size change, '05 Civic VP 5spd

I would like to replace my stock 14" steelies with 15" or 16" alloy rims. The reason for the change is cosmetic. I drive conservatively. Can I just install 15/16" rims or do I need to make other changes(computer,etc.) before installing bigger rims? I'm not familiar with rim sizes, such as 15" x 7.5". What are the rim sizes I should be looking for if I want a conservative rim size change? What tire sizes can I use for 15" rims.......16" rims? What effect will a rim/tire size change cause in my gas mileage or other performance aspects? Will my speedometer read incorrectly, and if so, how fast or slow will it read for a 15" rim...for a 16" rim? What are any upside/downside effects should I consider before making rim/tire size changes? Again, all I want is a sportier look.

Thanks,
Larry

http://www.tirerack.com can answer all your questions.