The 5 wire setup is not super hard. If your able to pull the new wire.
Just follow the picture for what color wire for appropriate function.
Not all HVAC need all functions so yours could possibly look different.
The blown in stuff super easy. Filled an attic in a home built in 1951. Just adding the attic reduced my power bill $50/$60 a month. Plus if you get 10 bags they let you use the machine to blow it in for free. Just get a good dust mask.
There is a newish product called Aeroseal. They spray a caulk type mist into your duct. Sealing from the inside out. Never used them but has been featured on many shows, also on a quick YouTube search has many videos.