I just bought and downloaded GTA IV and I will be getting this mod. What are some other mods that are pretty much a must have? Cars, skins, that type of stuff. Also, what are the tools I need to be able to download these mods?

First, welcome;)

Take a look at the downloads, there are many interesting emergency vehicles;)

For civil vehicles, skins, etc take a look at the pages here shown:

For installing them you need Spark IV, here's a tutorial about using it http://www.youtube.com/watch?v=Ef4aN_MYp_4

Also, the car mods uses to come with some lines in the readme, called "handling", "carcols" and "vehicles". These lines make the car mods running correctly ingame. For installing them, you have to go to your GTA IV folder--> common--> data, and look for some files called "handling" "carcols" and "vehicles", open them with notepad and replace each line of the car you're installing with the respective that come in the readme.

Then, if you install civil vehicles, you'll have an problem called Taxi Bug, that is that you'll only see taxis and police cars spawning. For solving that, you have to install a taxi bug fix, like Traffic Load, Traffic Flow (in the downloads section), or Traffic Control System, for example.

By other hand, if you want a more realistic police experience, you can install Dash Cam:

and First Person View.

Btw, for running LCPDFR, you have to install Patch 1.0.7.0: http://www.rockstargames.com/downloads#/?collection=9

That's all, I think, enjoy it!

Exactly everything I was looking for! thanks!