You should try and get an MRI scan done first, and allow time for the result to come back.
I had an MRI first, but the result didn't come back in time, so I had the TRUS biopsy. The MRI result then came back and said a TRUS was pointless and I needed a template biopsy (and indeed the TRUS didn't reveal significant cancer, which the later template biopsy did).
Anyone will be concerned about such a procedure first time. However, the TRUS was almost completely painless, and it's not something I would worry about having again if it was ever necessary.
Was given a couple of powerful antibiotic tablets (2 x 500mg Ciprofloxacin) about 40 mins before (to allow time to get into blood stream), and continued taking them for 3 days afterwards. (I seem to recall you have to avoid dairy products 2 hours before and after taking them, as dairy stops them working.)
You are warned you may get blood in urine, semen, and rectum. There was very little in my urine (only first time, and only in first few cc's). Blood in semen was much more dramatic, and if I hadn't read some other forums first, I would have been quite alarmed at the extent - bright red semi-congealed. Was told not to hold off ejaculating, although I waited 24h out of fear it might be painful, but it wasn't at all. After a few days, it turns brown (just as a bruise does), and it took 3 weeks to completely clear. Was told the blood is harmless if having sex with a partner, but out of politeness, you might want consider a condom. Also had some rectal bleeding after a large stool a few times over following weeks, and that area was mildly uncomfortable occasionally, but not painful.
They told me they would fit a catheter, but they didn't. Turned out that's only in case of incomplete bladder voiding.
Anyway, the procedure was a lot less significant than I imagined it would be. They are very good at preserving your dignity, etc.