Bellarte,
I had brachytherapy after about 7 weeks of field radiation (which was after surgery), and for me it turned out to be one of those things that sounded a lot worse than it actually was. By the time I had it done, I was already feeling some pretty severe side-effects from radiation, so I didn't feel as though brachytherapy made it incrementally worse. I was in an isolation room for about 36 hours (which meant that my husband could only be there for about 10-15 minutes during that time, and nurses couldn't stay in the room very long, either). All things considered, I ended up with very little discomfort while I was there -- the biggest issue was boredom! I slept, watched TV, and sipped on whatever liquids I was allowed to have. A few days after it was over, I was able to travel out of state for my nephew's baptism (I'm his godmother). Full disclosure: I was 39 at the time and had no other health problems.
Cathy