I was scared too. I had my surgery done by Dr. Marty Roitman in Newport--or maybe it was Huntington... I don't remember exactly; it was 10 years ago (I was 29). The only complication now is that I wish I hadn't done it because my husband of two years would like us to have a child together; I was single/never married with one child when I had it done. Why I did it is a long story, so I won't go into it here.
It sounds like you are doing it for the right reason. Five children is a lot. Especially with the age span you already have. You didn't mention how old you are, but if you have a 21 month old, you can pretty much figure you have another 18 years of mom-ing ahead of you. And at some point in your life, there may be a time when you want quiet time to spend on your own interests or hobbies, and/or time to spend maybe traveling and doing special things with your husband.
As for the surgery itself, it's relatively simple and recovery time is quick. I went in for the outpatient surgery in the morning and had a friend drive me and wait. I think it was only a few (2-3 hours) between the prep, the surgery itself, and the time spent coming out of the anesthesia. The doctor made a small 1/2 inch incision in the lower curve of my bellybutton, then filled my abdomen with some sort of gas (vapor not liquid), pulled the fallopian tubes out enough to tie silicon rubberbands around them, put them back in and sewed me up. I was a little goofy coming out of the anesthesia--repeatedly asking them when they were going to do the surgery.
The most uncomfortable thing about it was the day or two after while the gas dissipated into my system. I felt very bloated and a little crampy--like I had to pass gas, but couldn't. I was back to work at an office job the next day, moving around very slowly, still a little out-of-it, and in pain (not horrible, but achy). But I was a single mom, couldn't afford to take the day off, and my boss was a jerk, so I had to go.
As for the physical after-affects, I have a tiny white scar on the inside edge of my innie bellybutton. No one can see it unless I point it out. It didn't affect my periods or hormones/moods--I've always been a PMS monster and had heavy periods with hit-by-a-truck cramps. The best part of having it done was the liberation of knowing I wouldn't accidentally get pregnant again.
I don't know if I put your mind at ease, but I hope I helped give you enough details so you know what to expect.
Good luck. I think you are making the right choice.
Warmly,
A.