If u get the right sized battery for the car it will fit. Your alternator should last longer too. Just look in the catalogues provided in store. Cover the terminals in vaseline or petroleum jelly once installed also
Kinda as mick said, you can get a fully sealed battery which is legal and requires no vent (expensive but), or a battery with a vent. Using a tube, the vent is used to carry flammable gas (thats created during the charging process) outside the car.