How will you manage this step inside a wizard? Hard level: external plugins and valid signatures certificates needed

I'll try to explain myself as best as I can:

I need to create a flow for sign documents in bulk. I mean, the user selects in a table a number of documents, and then the user applies the sign to all these documents.

How am I managing that? With a fullscreen wizard:

1 step: choose the sign type (without certification -easy, add only your name; and with certification -the complex way, using plugins and this stuff)

2 step review the selection of the documents (the list with the documents ready to be signed, nothing complex)

3 step result of the action (signed or error)

So, my problem is in the first step, with when you select the "sign with certificate" option because:

-First, we check (automatically) if there is a browser extension installed. If not, we should redirect to the extension install.

-Second, if we found the previous extension, we show a list of valid sign certificates previously installed by the user. So the user selects one and continues with the wizard. OR, if the user doesn't have the signature certificate, we show the URLs to install one of the supported certificates

You can see here where all this should happen (low fidelity, sorry, haha):

I'm not sure how to add these things inside a selection inside a step. I thought of adding a spinner ie: "checking certificates". The result of this operation will be:

-No extension found: "You need to install X extension" -Extension found, but no certificates found: "You need to add any of these valid sign certificates" -Extension and certificates found: "Select a valid certificate"

In summary: spinner + required action.

What do you think about this approach? I feel that this is a complex situation :/

PS: Sorry for my English