BrianT -
Your standard backdoor Roth IRA is putting money into your traditional IRA, then fairly immediately converting it to Roth. The 140K you have in the traditional IRA is going to get in the way of this - you have 2 options:
1. Roll the money into a 401K or similar, zeroing the tIRA out before you do the backdoor Roth IRA.
2. Convert the 140K and pay taxes on it. Unless you spread this out over a long time (thus rendering the backdoor Roth IRA somewhat useless), you'll likely pay a lot of tax if you go this route.
Now, if by "401K Roth back door" you mean the "Mega Backdoor Roth IRA", that is a totally different procedure. The Mega-Backdoor Roth is wholly dependent on the terms of your 401K plan. You make after-tax contributions to your 401K (these are NOT Roth 401K contributions - this is important). Then roll those over to your Roth IRA as soon as possible. Not all plans even allow after-tax contributions, and even if they do, if they do not allow in-service rollovers, the awesomeness of the mega backdoor Roth is curtailed some. The IRS has provided guidance that these after-tax contributions can be segregated and rolled over separately, so you're not going to run into the pro-rata rule and get hammered with taxes, except to the extent there are earnings on the after-tax contributions.