Hey everyone,

First Post ever, so wish me luck and be kind please

Any ways,

I just recently aquired an 1996 Sc400 from my wife's Dad, he said he just got all the fluids changed and yatta yatta. I've been drivin it for about 2 weeks w/o an issue. Then started noticing that it took a little longer for the engine to start, but paid no attention to it, believing it was weather. After work last week I tried starting it and now it wont start, the starter turn's fine but it's like its not getting any ignition.
I changed the fuel filter hoping that would help, still nothing, but noticed that the fuel goin into the filter was nice and clean but the fuel coming out was dirt brown.
Got it towed and a shop took it for a week playing with the computer, I have no idea what they did to it, if anything at all, and charged me 500$. they got it running and I drove it home, but as soon as i started it up to go to work, it does the exact same thing.
I poured in some injector cleaner and let it sit for about 1-2 hours and my wife called the tow truck again, as soon as the truck arrives it starts up just fine, but i noticed a little bit of smoke coming out of the exaust, and it smelled terrible. I thought it was just crap getting burned out of the engine so i let it idle and dismissed the tow truck, after about 5min i turn it off to run inside for a minute, I come back out to start it again and now It's not starting again.

Any Ideas or help would be great, thanks for the help in advance.

details:
-Changed fuel filter "dirty as hell"
-Tried to start without an airfilter, no good
-Starter runs fine
-Shop took it, played with the computer, got it to run, as soon as i got home it wouldn't start again.
-Poured in injector cleaner in about 3 gallons of fuel, started once, smelled bad and wont start again.
-Checked oil, It's low, dirty and need's to be changed.