Need advice/help from record player gurus!!!

[T-Town Oil]

What is going on fellas? After constantly reading about people on here (and other sites) about there love for vinyl I was able to talk my dad into letting me have his old player awhile back.

He brought it back from S Korea after his service for Uncle Sam about 40 years ago. It is a Sansui SR-2050C Belt Drive turntable that plays 45s and 33s.

Today I finally hooked it up and it sounded like crap (fuzzy, scratchy and popping), but being persistent (or stupid) I took the cartridge and stylus off, cleaned them up and put them back on. I must say it sounds really great being hooked up with a pioneer elite sc-07 and being played with some aperion 6t towers.

My questions are these...on the back of the arm there is a dial that controls some weights. how do I know when I have it right and not pressing down too hard. I am also curious as to when do I know if I need a new stylus?
It looks like it has an audio technica AT125LC cartridge.

Thanks in advance for the stupid questions, but I really want to get the most out of this player if nothing else for sentimental reasons. Any advice or links for beginners is welcome!