if the tiles were fitted after the worktop, they are probably glued together with tile adhesive and grout. If you cut a slot in the grout under the tiles, to separate them from the worktop, there is a reasonable chance that some of them will not fall off.
I think the best tool would be a multicutter with a half-moon blade. An ordinary steel one will wear out, but you can get a carbide grit one. They are expensive so you could try, say, three steel ones.
Saxton is a good--value blade supplier, but high-end multicutters may use a patent head that other brands will not fit. If it doubt, tell them what tool you have (or are thinking of buying).
you can re-seal after changing the worktop with white or coloured silicone sealant.
If tiles fall off, soak them overnight in a bucket of hot water with a little household cleaner. Ordinary tile adhesive will soften and scrape off so the tiles can be reused.
Waterproof tile adhesive, as used in showers and floors, will not come off.