=) so how do i diagnose the problem my self?
Well, I have to say up front that if you have to ask then you may not be capable. It's not a personal slam, I'm just telling you what the deal is. Front ends can be tricky and if you're not mechanically inclined or used to working on cars/trucks then you probably should take the advise you've already been given and bring it to a shop.
Having said that, we need much more info before anyone can even begin to help you out. What year is it & what kind of shape is it in, what do you know about the history of the truck ? Is it lifted with larger tires or stock ?
The symptoms you describe can usually be traced to things like ball joints, steering boxes, track-rods, pivot joints, tie-rod ends and such like that. First & foremost are these things you're *able* to replace yourself ? If not then don't ***** around with steering componants and bring it to a good local shop. If you don't know what we're talking about then you probably shouldn't try repairing it yourself. I hate to discourage ANYONE from picking up a wrench but this is obviously a street rig and the consequences involve more than just your own personal safety, make a mistake here and you can literally wipe out a minivan with a family in it. A Bronco is a big heavy full-size truck and *more* than capable of completely destroying another vehicle & it's occupants. If you have a plastic toolbox full of screwdrivers and old sockets then take the advise & bring it to a shop. If you question their diagnosis the come on back & post it, we're happy to chat about it and offer advise but front-ends are serious business and the LAST thing that anyone here wants to see is you or anyone else getting hurt.