I agree with everything above. Especially the timing chain. It's unlikely you can even find a chain at a dealer that matches the quality of the original.
A couple of comments:
- My old '91 has 200k, and has always idled smooth as silk. But you gotta change the plugs at least every 20k, maybe sooner. Could be vacuum hose leaks, particularly to/from the IAC valve.
- The head gasket is indeed a weak point on some of the 103's, if you consider weak to be possible failure every 150K or so. The block is iron, the head aluminum. This sets up a sliding effect on the gasket as they heat and expand at different rates. Eventually the gasket will just wear down and begin to leak, most commonly coolant at the right rear of the block. It's easy to spot, certainly wouldn't do it until it indicated some symptoms.
- Valve seals are pretty notorious for creating oil usage on the highway. As stated above, they seem to fail sooner on cars that sit a lot. mine were eating oil before they were a year old.

DG