Echoing what John 2000 is saying, I want to suggest that you have a few contractors come in and give you an estimate for what it will cost THEM to do the job. As each contractor comes in, you'll learn more, therefore, you'll have more questions, and on and on. Once you've been through this process at least, then you can make a decision as to what you are willing to do and not to do.
Here are a couple of ways to save some $$$. DON'T mention this until you have your estimates. After you have your estimates, contact your contractor(s) of choice and see how much $$$ you'd save if you did the demolition. BUT, at the same time, you'd want to have someone who's a little familiar with framing a house! YOu don't want to go knocking walls down blindly for the contractor because you may be giving him MORE work to do. There is wiring and plumbing and possibly 'special support' behind walls and such. If you 'bust' something, well, you'll be spending the $$$ you were trying to save. Also, ask them if YOU can buy the appliances and fixtures and such. YOu will save some $$$ here. And lastly, you can do things like priming and painting. Do understand that if you do demolition, you'll be responsible for the disposal of whatever you remove (unless you can work out an agreement w/the contractor to use his dumpster.) You'll have to do a lot of leg work to shop for things. And lastly, you'll want to read up on 'how to paint' because, like everything else, you want it all to look right and last. You have options when it comes to painting a kitchen vs. painting a family room so keep this in mind.
Oh, as for that weight-bearing wall, don't mess w/it. There are code issues that are waaaaaay beyond the scope of this Forum. Leave it to a pro even if you decide to do a lot of the work. And to reiterate what John said, if you have to ask the kind of questions you're asking, you may be in over your head. Buy yourself a Kitchen and Bathroom Remodeling Book. Time-Life and Reader's Digest have them. Border's Book store has them too, I believe, and you may want to search the on-line Book Stores too. There are magazines like The Family Handyman, Home & Garden, and the like to give you ideas and somewhat of an education. Heck, try the library! My best to ya and hope this helps.