hi how do i fit a lower gear lever

hi
my defender 300tdi has some jobs to be fixed
i want to do jobs myself and learn and buy tools as i go.

the lower gear lever part number frc8724 has broken a lug on right side.
gears go in fine just hard to find one now and again.

how do i go about it and what tools do i need

also i want to change headlights as they look rusty which to buy i have seen
pairs starting at £20.99 pair up to £120 quid do i just go with the cheap ones.

thanks
marc