1995 Mazda 626

Noises problem
1995 Mazda 626 4 cyl Front Wheel Drive Manual 200K+ miles

I have a 1995 Mazda 626 - 2.0 L, 4-cyl with 200K+ miles. I have taken VERY good care of it - but it is very old. I just need it to last until I graduate from school. Within the last 6 months or so, it has been making a "clatterring" sound, when I accelerate on the highway - or when there is a "load" on the engine, as when the highway starts to go uphill. It almost sounds like a "loose" valve tappet, on one of those old v-8's - or that it needs a valve adjustment? - But I don't think that it has valves that can be adjusted, does it? Any thoughts or ideas would be greatly appreciated. Also, I am trying to find a place on-line where I can get a free download of the sevice manual. Any ideas?