replacing floor tile in laundry/ utility room

The 30 year old tile in my laundry room is cracking and coming loose, so I would like to replace with some simple to install peel & stick type vinyl tiles. The floor is cement and I can see swirls of black glue from the old tile. I assume I have to get the old glue off and have the floor as smooth as possible before placing the new tiles. What do you recommend for removing the glue and cleaning the floor and special scraper tool? The room also holds my furnace and hot water heater on one side if that matters (I will probably leave the old tile under the heater for now...); I'm guessing this would stop me from placing any type of under layment. Is there something I should "paint" over the old floor (to cover up any glue remnants) before attaching the new tile?
Phil Tomaskovic
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