1. She'd like to have a face-lift.
她想做个面部整容手术。
还能这样说：
She wants to have a face-lift.
She has a desire to have cosmetic surgery.
谚语：
A fair face may hide a foul heart.
人面兽心。
2. I think it's time for me to do plastic surgery.
我想是做整形手术的时候了。
还能这样说：
It's time to have a face-lift.
It's high time for me to have cosmetic surgery.
应用解析：
a plastic smile 假笑，强笑；
plastic clay 塑性粘土，陶土；
a plastic figure 塑像
3. I want to have a plastic surgery to change the shape of my mouth.
我想做个整容手术来改变嘴巴的形状。
还能这样说：
I think a plastic surgery will make my mouth more beautiful.
I want a plastic surgery on my mouth.
应用解析：
get (oneself) into shape 为健美而长期锤炼等。
例如：I do yoga every day to get myself into shape.
我每天做瑜伽锻炼身体。
4. I plan to have a face-lift to tighten my face skin.
我计划做个拉皮手术使我脸上的皮肤紧致一些。
还能这样说：
In order to get my face skin tight, I plan to have plastic surgery.
I make a decision to do plastic surgery to tighten my face skin.
应用解析：
tighten the economy 紧缩经济；
tighten up 密封，拉紧；
tighten one's belt 束紧裤带；节约开支