How do i fix my nokia 6680 and can i send my inbox sms to the memory card instead of internal mem?

my 6680 has become very slow lately and sometimes just reboots at random.I was told it needs to be flashed. can i do the flashing myself and where can i get the software? i have been using a bluetooth dongle to connect to my phone,can it be used to flash?also, had 1000+ msgs in my inbox but now,when it gets to 250,it says mem full!