HTH SCI 1PA3 is marked on a pass/ fail bases. Do I still get the 3 units from it though?

Yup, you'll get a credit, but it will just read 'Pass' on the transcript. 0 units are non credit courses.

I read on some forums that grad schools look down on summer school because in some schools, the transferred credit becomes a pass/ fail basis.
so is it still good to take this course?

Hmmm, it depends on the program. I know in MSW programs they'll use as many credits as needed to make up the last two years of GPA, no matter when they were taken (such the case for part timers), and if you took a course at another school they make you send the transcript over so they can see the grade.

It shouldn't matter. That's not why summer school is "looked down upon" (and that varies by school and program) as generally when you apply places you have to provide every transcript from every post-secondary institution you've attended to the place you are applying. The course won't count towards your GPA (unless of course you fail), but I don't know any school that doesn't count the credits.