HI Shawn,
I have successfully 'incubated' milii eggs at room temp (damp vermiculite or moss in a sealed container), but Im in Qld. I have also successfully used a heat lamp with a thermostate set up in a wooden box.
There are a number of ways you can make your own incubator - I suggest doing a google search on "home made incubators" to get a few ideas. some people have used old bar fridges with a fan and heating cord, which I believes works very well too.
I ended up getting mine off ebay for half the price one from the manufacturer would have cost me.
And yes, 28C is a good temp for levis and milii.
cheers,