>Can I edit the message using a pc's serial port and software like VB?

Yes you can.

>What pic micro will I use?

16F628, 16F876 etc...

>What pbp command will do such that I can save all the characters in the alphabet and retrieve it (say each character represents five bytes) so that i don't have to change the the values in the lookup table every time I want to display a new message.

Well, if I was approaching this task, I would save my display message in the PIC's internal EEPROM, but I would use an external EEPROM (eg 24LC16, 24LC32 etc) to hold my character font - because if you were to replicate the ASCII character set between say $20 and $7F that would be 95 characters*5=475 bytes. Also changing character fonts for different applications or languages then becomes as easy as plugging-in a new EEPROM. As for PBP command... Read, Write and Data would be used for internal EEPROM, I2CREAD and I2CWRITE for the external EEPROM.

Melanie