Hello. I am going to change out my shower stall and my house is pretty old. I just need to know the basics on how to install the shower pan and is there anything that I should be made aware of before I tear out the old pan?

The first thing to check - to confirm if it'll be a smooth job - is that the location of the drain hole in the new one will be in the same place as the old one.

After that it's pretty much a breeze. Most of them come with decent installation instructions that will confirm so.

... and be sure to measure three times before you cut into the sides - where your fixtures will come through ;)