代わりと言っては何ですが、・・・私が、いささか、ご指南いたしましょう。

、・・・、、。

I hesitate to call it a substitute, but... allow me to offer a little humble guidance.

Literal

Substitute [quotative-と] say-[if-ては] what [polite-です][but-が], ... I [subject-が], somewhat, [honorific-ご]guidance humble-do-[volitional-ましょう].

The opening 代わりと言っては何ですが is a stock polite hedge — literally 'if I say substitute, it's what... but', meaning 'it's hardly much of a substitute, but...' — a formulaic downplayer used when offering something. いささか ('slightly, somewhat') is literary and adds refinement. ご指南いたす is humble-language (謙譲語) in the ご~いたす frame, lowering the speaker's action of offering guidance to the listener. Together with ~ましょう (volitional 'let me X'), the whole utterance sits firmly in keigo, typical of an elder teacher or an old-fashioned fictional voice.