Hi, Rather than change the tyre, assuming it's still legal, why not just get it repaired? if it's in the centre to outside edge of the tread you can get it plugged for much less than a new tyre. As to a chain splitter read your Haynes manual and it tells you how to remove the side cover of the engine to get at the front sprocket, an easy job to do as long as you take your time and follow the instructions, remember it's NOT a car you can't just do the bolts up till they squeak you need to do them up to the correct torque..! Usually the rear and front sprocket are changed at the same time as if one is buggered then the other one is probably shot as well so buy a set. Wemoto has a good rep for parts and they are usually pretty good on price to. Good luck.
One other thing it's usual to say "Hi" in the new members section just so folks know your serious about the site and not just looking for free info. Just sayin..!