I wanted to know how to replace an ingnition switch on a 1995 Toyota Avalon

Do not attempt this repair if you are not qualified to disable and re-enable the SIR system.
Do not attempt this repair if your vehicle has onboard anti-theft unless you have the tools to reset that security system.

Remove upper and lower steering column covers.
Place ignition switch in OFF position, then disconnect ignition switch connector.
Remove four retaining screws and ignition switch. If necessary, remove lower steering column.
Reverse procedure to install. Reset stereo and anti-theft system, if necessary.
On models with coded stereo anti-theft systems, refer to Technician Safety Information for code procedures.