When I got the car I was told I had to replace 1 of the soft plugs close o the starter, problem is i've never done this, how had is this going to be?

 

not enough info provided
car, year, model, engine, etc
...

 

OK, let me just say first off, i don't know sh*t when it comes to cars. That being said I know it is a 69 Cadillac convertible, I'm told it is the original engine. Sorry for the lack of info.

 

easy .. drain coolant 1st..

on those engines of past years, the hardest thing was getting access to the
soft plug, punching it out with a chisel and prying it out - dont damage the block.

clean out the seat for the plug, pop new plug in with proper bonding agent,
tap it slightly with soft hammer - i like leather hammer ..
sorry .. cant remember what the bonding agent was.