hi all. tried to start the micra this morning and the battery was dead. had it for about 2 weeks and this is the first problem ive had. i know i didn't leave any lights on or anything. i managed to get it started with jump leads then drove it 15 miles and left it for a about 9 hours and the same problem again. i haven't had any other problems after getting it started that's why i think its the alternator. how easy is it to change one?