I agree w/Steve:. I'll just say the same thing another way.
First off, if the floor is essentially flat BUT has some dips in it, then SHIM from underneath. If the floor is NOT essentially flat but truely UNEVEN, you may need a new subfloor. Since it sounds like the latter type of job is a bit over your head, I'd highly advise that you hire a Pro to do the prep work. If the prep work is messed up, your finished floor will show the imperfections AND probably start 'popping' up all over the place. Sometimes, hiring a pro is the best thing to do.
Assuming the floor is level, then you can install what you want. There are ALL kinds of flooring out there. But before you buy anything, I suggest you get a copy of the WARRANTY and the Installation Instructions. Yes, both of them. FIRST, that information will give you an EXCELLENT insight into what you need to do to do the install AND how you'll be 'covered' in the event you need to file a claim. I say the latter because IF you don't do the prep work correctly, you WILL end up filing a claim. And if your prep work wasn't done right, then forget being covered. SECOND, that information will even tell you if you can install the particular flooring in the 'conditions' in your house. For example, if you're installing it over a damp crawlspace, the paperwork will 'point out' to you if that's OK. It may not say it directly but it will ILLUDE to that point. Do you know what I mean?
My best to ya and hope this helps.
Jay J -Moderator
PS: You should be able to get the info from the Retailer. If not, then ctc. the Mfgr. of the flooring you'd like to install and get it from them. The WEB is a great place to start ...