1996 Chevy Lumina isn't working correctly.

First let me say, I am a 20 year old
girl who knows VERY little about
cars! I inherited this car from my
grandma. It has less that 47,000
miles and everything original. I was
driving it normal, like I always do &
whenever I hit 30 mph I noticed it
making a weird noise. When I tried
increasing speed it wouldn't increase
speed and started making a noise
(sounds like when your cars in park
and you hit the gas.) so, I pulled over,
and restarted my car. It started up
fine and at about 20 MPH it started
doing the same thing. When I
stopped at a stop light and began to
drive again, it got up to 40 and then
started doing it again. I have no idea
what's wrong. I always seem to get
taken advantage of at Mechanic
places because I'm a girl and know
very little, I think they always fed me
a line of bs with my previous car. Any
ideas what this may be? Or what I
should say when I take it in? I WILL
NOTE, I was about to get an oil
change! My check oil light was on
the past few weeks, my dad put oil in
it and told me to get an oil change,
but the oil light went off so I went out
of town the past week (not driving
my car) and planned on getting it this
weekend. If you thin you know
what's wrong, could you please tell
me how much you'd guess it'd to
be? Thanks.