I am going to try the WILD technique sometime soon, but beforehand I want to know more about sleep paralysis. First, how long does it usually last? I’m kind of afraid of experiencing it too long and getting panicky. Is there any way to get out of it, or do you just have to let it pass? How unpleasant is it?
That’s good, always study what you’re gonna try before you do try it, that’s my policy. 
It may vary from person to person, but with me it usually don’t take more than a couple minutes till I ‘lose’ it or get into a dream.
Well, first have in mind that it’s all in your mind. You can get scared the first time, but it’s normal, just don’t panic and you’ll enjoy it.
I only tried to get out of SP once, I started moving like crazy but it was useless, so I just stoped, focused and said to myself “this SP will end now…” and it was over, after repeating this a few times.
The first time it can be a bit scary, but then it just gets more and more fun when you get used to it. Just don’t be afraid, there’s nothing to be afraid of anyway 
How long does it last? Depends. For me, it lasts up to a half minute (or it feels like it… I heard time tends to pass more quickly in SP).
Is there any way out of it? Well, many people are able to wiggle fingers/toes/move their eyes during SP. I keep moving these parts until I get out of it, or I just fall asleep into a WILD.
How unpleasant is it? Scary the first time. After the first time, it’s not scary. It’s quite interesting, in my opinion.
But don’t let any thoughts about SP hinder you from practicing WILD. From what I’ve experienced and heard, SP doesn’t happen very frequently while WILD’ing, so you don’t have much to worry about.
Hehe, just don’t be scared. First time I felt it, my body seized up, and felt like my entire bed was spinning…got too excited and it stopped. lol I thought it was actually pretty awesome. And after that, I just stopped fighting it, and lay back and enjoy it. Haha, it kinda tickles for me 