Since how hard the swap is, is a subjective question, my subjective answer is not really hard, probably a 4 or 5 out of 10, 10 being hardest. Of course when you start doing the swap you may think it's an 11 halfway through, or a 2. Working under the dash adding the pedal set isn't fun, neither is tracking down and assassinating any electrical gremlins that are going to pop up. Yes, you'll need to swap the correct rear mount.
Are you going to have a time table? As in you have to have the car running within a week? If so, my advice is either scrape the idea, or get an automatic B16A tranny, and mate it to the B18C and have a fun auto.