Convert String to Number in CRM

Convert String to Number in CRM

I have a picklist that I need converted to a number and then used in a custom formula. Is there a way to do this?
Or, is there a way to use custom formulas, in a new formula?

This is used for a custom qualification process.
There are 8 categories of qualification, including: budget, need, authority, timing, etc..
Each level of qualification corresponds to a number: 0-5
Instead of using a number, we use text so that we can clearly describe this range: 0-5
Each category of qualification, corresponds to a particular weight.
I use those weights to come up with a simple % probability.

I can use a series of "if" statements to create a number for each category, but I found out that I cannot use one formula field, within another. I'm not sure how to move forward.

I want to add result of custom formula 1 & 2 into a new custom formula field. Is this possible?
Is it possible to change a string to text in CRM?

Thanks