I would like to withdraw money from my 401k account and invest it in certain stocks. Would this be treated the same as if I were just withdrawing the money to get the cash?

You need to talk to a financial planner before you do that I believe any withdrawl even if it is to reinvest it has a serious tax penalty. The only time I don't think you get penalized is if you roll it over into an IRA Traditional 401K to Traditional IRA, Roth 401K to Roth IRA.

If you are still working at the company where your 401(k) is located you really have no recourse on this - you are pretty much stuck with whatever investment options the plan administartor has made available in the plan. But if you have left the company, then you can do as Camborio suggests - roll your old 401(k) over to a Rollover IRA and start managing it yourself.

Make sure you investigate your IRA options so you get the one that is the best for you. This is where finding a good financial planner comes into play, because they will ask you various questions, such as what you want to do with your money, and when you're planning on using it and how aggressive or conservative you want to be in your investments. If you have time to investigate yourself then you can save some money, but I don't have time so I have my Financial planner who helps me out so I don't have to become that well versed in the legality and tax ramifications of it all.