Lipos are great, but they mustn't be discharged below 3v per cell so a 'cutoff' on your speed controller is receommended. In terms of connectors, the majority use 'deans' style connectors as they are the most reliable, could you describe the connectors your's currently has?
What's the make and model of the charger you have? Someone will be able to let you know what it's capable of.
Tyres, as SLD says the majority of people running Sharks in the UK (where are you?!) use touring car wheels (12mm hex) and schumacher rally blocks or some run foams. If you are just bashing then some hardwearing tyres would be better, you need to find out what works at your local club before buying some though! Also, you may need to check your gearing if you increase the diameter of the wheels/tyres.
For more information on the Shark (and the Blaze, Vendetta, MB4) check out
www.uk-microrc.co.uk It is uk based so if you're not then the setups etc may not be so suitable.
Apologies if it's a lot of info, but have fun!!