It's heavier and messier than it is hard. Roughly:
1. Shut off the water, flush, and sponge out what's left in the tank and bowl. Have old towels down.
2. Disconnect the supply line, take the caps and nuts off the two bolts at the base, rock it gently and lift it straight up.
3. Scrape the old wax off the flange and stuff a rag in the pipe so sewer gas and dropped bolts stay out of it.
4. Check the flange isn't cracked or rusted through. If it is, fix that now, it's the bit that causes leaks later.
5. New bolts, new wax ring, take the rag out, and lower the toilet straight down onto the bolts so it doesn't smear the wax.
6. Tighten the nuts a little at a time, side to side. Stop once it doesn't rock. Overtightening cracks the porcelain.
Measure from the wall to the bolts before you buy. Most are 12 inches but not all, and the new one has to match.
