I got a used Medela breast pump (replaced all of the parts), and it didn't seem to work very well either. It worked well enough that I couldn't justify spending the money to buy a new one though. On vacation, I borrowed a newer model Medela (using my attachments) from a friend of mine and it worked so much better! I'm not sure if the newer models have better technology or if mine was just so old that the motor was worn out. Anyway, I guess my point is that you might want to try getting a new one, although I know how expensive they are and you mentioned being on a tight budget so you'll have to decide if that will work for you.
As far as getting help...there should be lactation specialists at the hospital where you are going to deliver. While you are in the hospital, I don't think they charge to come and help you, so I would use them as much as you possibly can while you are still there. Once you leave, they should give you the number for the lactation specialists at the hospital in case you have any further questions. I called a few times once I left the hospital to ask questions and they never charged me anything for those calls. Also, I have never used them, but I think you can find a website or some information for the La Leche League. They may be able to help you find some help if you need it.
I'm editing my response because I noticed someone else mentioned a shield. I used this also with my daughter and while it was a bit of a pain to use, it worked for us. I am not sure I would have been able to nurse her without it. I am hoping that I won't need it for the next one, but at least I know it works if I do!
Good luck and congratulations on the newest addition to your family!