well, it's normal that uploading programs won't work when you've got RX of the board connected to your receiver. the RX and TX pins on arduino are more or less directly connected to your serial lines that go to the USB port.
i don't know if i fully understand what you're trying to do.
you want to receive serial data on arduino, but who is the sender?
for debugging, i propose, that you connect BOTH the transmitter and receiver to the SAME arduino board.
receiver> RX
transmitter> TX
and then have an led (on pin 13) blink whenever there is serial data arriving.
the board should receive what it sends now. you don't have to care for the baudrate settings on your sender like that. just start with 9600.
TIP: to test the code, i would suggest leaving the transmitter and receiver out. just connect RX and TX on arduino with a jumper cable.
if arduino receives "something". you should re-write the code to see if it receiving the correct date.
for example: if the received byte is a "5" light up the led on pin 13.
hope, i didn't misunderstood you.
your pdf/ data sheet wasn't very helpful. can you post the product link to conrad?
//kuk