Ok I got it put in today.
It was fairly straightforward with no real surprises.
I first drained the antifreeze out of the radiator and out of the block. In case you don't know (I didn't until I was reading through my owners manual the other day) there is a drain for the block on the right hand side of the engine a few inches below the fuel filter.
I then took off the suction manifold. I was a little worried about this because I didn't know how hard it would be to get off and put (a new one) back on and I wasn't sure if I would end up with 6 gallons of hydraulic fluid on the floor.
Turns out they come off and go back on really easy. There is also very little hydraulic fluid in them when you have the tractor shut off. I think I ended up losing maybe a few tablespoons full. The manifold has a spring inside of it to keep the hose from collapsing. I was not aware of this but it was easy to take out of the old one and put in the new one.
I then prepared for the worst when getting the plug out of the block. My tractor is 10 years old and had 2000 hours on it.
I didn't have any trouble. I used a 2 foot long breaker bar and a 6 inch 1/2" drive extension. I used moderate pressure and the plug popped loose.
I then put Teflon tape on the heater threads and put it in the hole. I noticed that the heater was made in the USA. EVEN BETTER!!
The only trouble I had was trying to get the heater tightened into the hole. I used a channel lock wrench perpendicular to the bolt part of the heater to get it tight. There's no room to use a wrench properly. It doesn't leak (I drove it around the yard to test it) but I would like to get it about a half turn tighter. I'm going to buy a claw foot wrench to get it taken care of.
Here's what the final result looks like. It took me about an hour from start to finish. I plugged it in to test it and after about 10 minutes the plug was too hot to touch, so it's doing something. I guess I'll find out how it does this winter.