Well i have restored my 1989 Suzuki trail couple of months ago but i am more like a DIY sort of guy so i went for professionals only for the stuff/tasks that i could not do at home like getting the paint work, boring the cylinder etc
If i were you, i would have downloaded the service manual and learn more about this bike, you can Google and find a lot of information on this bike even people doing same restoration as you so you will find out how you can proceed.
Two stroke engines are very simple to work as compared to 4 strokes. As you said it is running so i suspect you can get away with the engine work but you can just pop up the top end and see the condition of piston and cylinder. If the cylinder is scored you need to get the cylinder re-bored and replace the ring piston as well in most cases. This thing can be done at home with some basic tools and a service manual. (Except Cylinder work)
Bottom end is a different story, ideally you should do the leak down test to check that crank seals are holding as most of the time these old 2 strokes machines have leaking crank seals. For this part you should go to a mechanic as you will need some proper tools to get it done.
Rest of the stuff is easy stuff, getting the paint work, wiring issues, wheel bearings, handle bearing, changing cables etc
Anyways now i will come to your questions
I live in multan so i can't guide you any good mechanic but i am sure there will be many two stroke mechanics in lahore, you can check macleod road or wait as some one will suggest a good mechanic.
You to need to look out for the parts, depending on your budget, in my case i found some parts from china but most of the parts i imported from Japan. You can visit www.megazip.net (Japan), www.aliexpress.com (china), ebay and amazon for US/UK. I am not sure about local availability of parts for this bike.
Restoring the cosmetics and electricals and minor stuff will not be an issue so i would say get those done and for engine related work if you are able to find parts then get the engine work as well. If you can't find engine parts and engine is almost dead then swapping an engine is also an option.
I hope i have answered some of your confusions/doubts/queries. I would encourage you to go ahead with a restoration as it's a complete running bike so restoring it back to it's original (or near to original) glory won't be any issue.
If you find it hard to do or you can't find time then you can always sell it as it is and let the new owner take care of it.