I need to replace my radiator is this a complicated procedure for me a novice?

Not at all its very basic With the engine cold remove the lower rad hose and drain the coolant {this can be recycled by straining it with a fine screen {panty hose works fine]remove the top hose and loosen the rad mounts.Make shure the ign is off and remove the rad cooling fan and ac bolts [if fitted].remove the thermostat and flush the system with a regular garden hose until its clean.You should replace the thermostat with a new one [only a couple of bucks but a must do on an older car]
fit the new rad [tip last off -first thing on]and connect the hoses refill and top up your coolant.Start your car and allow to reach normal working [let it idle until the rad fan cuts in and out a few times and hey presto yoy saved yourself money and repaired your own vehicle [well done]

I must add that a thermostat on a 2004 Forenza costs about $85 and must be bought from the dealer, otherwise its as he said.