How painful a sweep is depends very much on who does it in my experience. I have had 4 to date (two last pregnancy and two last week).
Sweep #1: Uncomfortable but not unbearable. Very very quick. Achieved nothing. Done by very new (trainee?) midwife at hospital.
Sweep #2: Very very painful. Lasted a couple of minutes (which is quite a long time when someone's rootling in your nethers). Achieved lots of cramps and aches and a slight show. Done by more experienced midwife at hospital.
Sweep #3: Very painful. Achieved nothing. We can discount this one though because my horrible useless midwife did it and she was rough and had huge hands and told me there was nothing to stretch or sweep and turned out to be wrong. Her horrible stubby little fingers just couldn't reach. Or she couldn't be bothered. Horrible.
Sweep #4: Uncomfortable but managable. A bit painful. Lasted about a minute. Successfully separated membrane from something or other. Done by lovely consultant at hospital.
You don't have to have one if you don't want one. It's worse than a smear, but different than a smear too. Smears make me feel a bit sick, but stretch & sweeps don't, they just hurt.
Have only been induced once (and will be again tomorrow). It was pretty hard, but that's because despite being 3+ weeks overdue my body wasn't remotely getting ready for labour or birth. I think induction if you're nearly there anyway isn't so bad. You'll have to have an internal examination anyway to establish if you're getting there. Plus induction inself involves various people rootling in your fanjo eg to administer pessaries or break your waters or just see how you're doing.
Sorry not to have posted the most cheering message. Honesty best policy and all that. Plus my experience might be very different to yours. Good luck and I wish you a spontaneous labour! (You can have mine if you like as it's clear I'm not having one!)