In an awkward position (job related)

I interviewed for a position internally back on June 14. About three weeks ago the hiring manager had me come into her office promptly at 8:45 AM or so when she arrvived, told me I was a top candidate (she was hiring for two of this position), and asked me about training for my current role going forward and how that would look - first of all I thought this was awkward as training for my current role should not be her concern but my current manager's/the CFO/controller/anyone else.

But I guess it's that whole team atmosphere where we are all under the umbrella of Finance so she doesn't want shite to just hit the fan when I leave my role, and some of this may be coming down on her from the CFO himself.

Either way, I am worried about actually being able to perform well in this role (data analysis).. I haven't had to do a lot of extensive stuff.... ever, in Excel and now I will need to know this stuff. Mostly pivot tables (which I can set up), but then making very professional/presentable graphs from the data and throwing them in powerpoints, etc for presentations for the CFO/whoever else.

I've started looking at stuff to train myself prior, and getting kind of psyched out that I won't be able to do it, and that maybe I gave off the impression in the interview that I was better at Excel than I really am. I was, however, honest that I had no SQL or SAS experience, and even said I had not used PowerPoint in forever.

I think even if I was a little more honest on Excel I was probably going to be the choice anyway, because this is a state job and you have no idea just how bad some of the other candidates can truly be - and I'm generally hard on myself.

But now I am hearing from my OLD agency and the hiring manager under Budgets there wants me to apply for a job that closes July 31. A lot of changes have happened at my old agency and people are sort of flocking back as the CFO is better, etc.. I worked very well with this guy before and I know it'd be a breeze under him.

But that puts me in an awkward spot where I am currently at. Already my current boss knew I interviewed because since it was internal I basically felt I owed him that courtery. And I have seen the controller/others under our direct line be a little different toward me since.

Now if I tell this other hiring manager I won't be accepting her offer whenever that may come, then I have to deal with that awkwardness until I get offered from the old agency.

Essentially... do I take the role in which the offer is coming soon for better career opportunity/advancement/challenging myself - or go back to the old agency where I'd be more familiar with that role and really probably not have to learn anything new? I am leaning towards the former...