Hello viewers from Australia.

I've just recently purchased a Mercede's 250se auto 1968 with 110 miles on the clock, from a friend who said the gear box had gone,it engages all gears but just no power.

The engines not running great at the moment,i've cleaned(not replaced)the plugs,cap & leads,the plugs we're black when i took them out turned the car over seems to run better but it's still missfiring & puffing out black smoke & spitting.
Could it be the electrics?
Should i buy new points/leads/plugs & cap & change oil & filter.
The engine has no power it runs in high rev's then warms up then stalls.
I don't think the gear box has gone i think the car needs a good tune up, please could somebody give me some good d.i.y tips on tuning this car up & getting it to run like the true classic it is.

Thanks

Rick

Australia.