Regarding the 3-pt implement, they are usually secured with linch pins; if you have a county Ag coop near you, a CNH dealer, or a Tractor supply, you can buy 'em by the bag for less than a dollar each.
There are several REALLY good articles on this web site about how to use a 3 point hitch and not get yourself killed. I was just about where it sounds you are about 3 years ago, and reading those articles let me do stuff MUCH more safely than I would have on my own.
Regarding the carb, theres many smarter folks than me here, BUT you'll need to ad some more detail to help- when is it leaking, and from where?
hope this helps