Pertinent info:
(House is in Maine, so frost heaving is a consideration.)
The front entry has an original (1956) brick/flagstone (over concrete) stoop, which looks very ratty. Over the years, it sank into the ground and tipped away from the house a bit, but we believe we have eliminated the cause of that: For many years, there was an improperly filled old septic tank near it, which created a huge sinkhole of water. That part of the yard was horribly waterlogged. We had the septic tank dig and filled properly, and the yard is dry now, so hopefully sinking will no longer be an issue. Here's a photo. What you can't see is the crack along the house edge (filled by a PO with masonry caulk). It's also tipped forward a bit and sunk into the ground.

Ideally, I'd like a somewhat formal bluestone stoop out front (in contrast to the frame & decking porch on the side entrance.) BUT..... we're DIY-ing this on a tight budget. Sonotubes and framing and porch decking are a known quantity for us, but we've never built a bluestone stoop. I looked it up online but not sure what method to use. Would we need to completely remove the existing stoop, excavate below frost level, and build a big concrete form with bluestone on top? Could we use the existing stoop as a base, building it up a few inches and applying fresh new facing stone? (I think I'd prefer a rectangular shape to the rounded, but could live with round if easier.)

Is the bluestone option just going to be way more difficult and costly? I have about 9 months worth of exterior projects to try to cram into our short Maine summer, so this one thing can't take up all my time and resources.

What would you do?
What would you recommend?