I’m running an Octopus 1.1 board in my printer that once was a Taz 6.
If you have never configured Marlin before, it’s a good time to learn, but this is also a good time to add a few upgrades. You’re going to have to extend several wires to meet the locations on the Octopus board, but you can avoid all that headache by also upgrading to something like the Hermit Crab quick connect toolhead system, since it includes a new wire with all the length you need for the toolhead connections.
I went into some detail on this post: Upgrading Taz 6 - what are my options? - #2 by Wrathernaut
But bottom line: Octopus board, hermit crab, and (potentially) a new 1.75mm extruder setup, you’re looking at around $250.
Just doing the board, BLTouch, and wiring it yourself, about $80.
How much do you want to put into the aging Taz6?