Hey everyone. Just started playing RCT 3 again after about 3 years of being busy elsewhere. Was starting to get a little bored with the standard stuff they have but then found the joy of custom scenery; and now the game is a blast again!

I am having a bit of trouble finding a couple things I want to use in my new park however. I am looking specifically for a rail road crossing gate, and road signs (I want to use go karts, but I also want to make sure they don't look like crap).

I have used the search function, but it wasn't a lot of help.

Welcome aboard oldman! lol
I just started up again myself a few days ago.
Funny how quickly my MODS folder has become so much larger than the game folder.
Anywho, do a google search for RCT3 MODS and your bookmarks will be just as full as mine.
I found this for you, hope it helps u out:

Get it here:
Vodhins Gizmos

As for the go kart... I know there's some sort of mod out there for it.
I've seen it but didn't grab it yet. There's a track set on this site for it also.
I've actually just DLed the "Invisible Track" mod and was going to experiment with that.

I believe what you're reffering to as "mods", we call CC, or Custom Content.

Types of CC:
CS - Custom Scenery (Most popular of them all)
CTR - Custom Tracked Ride (Changing what coaster trains go on what track, also can make custom trains in Blender)
CFR - Custom Flat Ride (Like a carousel)
CT - Custom Track (Track pieces normally imported from No Limits to make smoother rides)