I was a little shocked to find out that the cheapest block heater for my car was from the dealership and it screws right in to the block.
You can also get
dipstick oil heaters, only 90 watts but that should be enough to thin the oil and get everything warming up quicker, they replace your dip stick so there is no way to really screw up installing one or removing it if you don't like it or want to move it to another vehicle.