>I am about to start my first Pic Project. It is a small device that
>should
>
>  (1) accept digital data (numbers & strings) from a Measurement device
>via RS 232 at  any time.
>  (2A) store the Information in memory (approx. 20 Kilobytes of data)
>  (2B) display the latest aquired data on a LCD display
>  (3) send all data to a PC via a second RS 232

PICs are great little controllers, but I would not use them here.
The main reason is the lack of two hardware UARTs and the limited capability
of handling large amounts of RAM or EEPROM.  If you choose serial EEPROM
you get an expensive solution, if you choose parallell RAM the interface
is a bit complicated (PICs from the 16C-family).

I assume your "Measurement device" delivers data without any particular
protocol or flow control.  For the transfer to PC you need a safe protocol,
which is up to you to design,  and this takes quite an amount of code in the
microcontroller.

Choose Dallas 87C520 microcontroller.  This one has good power management
capabilities and two internal UARTs. It has 16 kByte EPROM which ought to
be more than enough for your application.  You can easily attach parallell
RAM of desired size, 32-128 kByte.  Or you can use flash memory,
e.g. AMD Am29F010 (131,072 x 8-Bit, CMOS 5.0 Volt-only, Sector Erase), for
power safe storage.

The main snag might be that the are no really cheap programmers for this
processor.

Best regards
Thomas