I agree the more mAh the better, it will last longer
Not sure on the charger, it really depends on the charger. If the charger just charges for a specific amount of time then shuts down, then it can be charged, but will not get a complete charge. If the charger charges the battery for a specific amount of time and then goes to a trickle charge, it will fully charge the battery, but may take along time to completely charge. If the charger charges untill it detects resistance (probably not th proper term, but you get the idea) and then goes to trickle charge, it will work like it did with your previous battery.