What does your anonymous RF module use? My XBee shield allows choosing 0 and 1 or 2 and 3.
Is there enough PIN?
Yes.
Are they using the same PIN?
Can’t answer that for your RF module.
Do you know an “arduino like/compatible” board already built whith ethernet and RF ?
As far as I know, there is not one. There are Arduino boards with ethernet built in, but no board with RF, too, since the RF modules vary widely in price, range, ease of use, data integrity, and many other factors.