Questions about my 87 cabrio

So I have joined the ranks as cabrio owner, but i'm still getting to know my car better.

Its a 87 cabriolet rabbit (what previous owner told me, is that even possible?), manual transmission (prob newer), inacurate odometer, good shape all around, runs great, slightly leaky top, suspension shot and squeaky, new minor parts here and there. Previous owner left a bit of tinkering and small projects. All around solid car, just needs a little tlc.

Q 1: I don't think the engine and tranny are stock, how do i figure that out?

Q 2: I think it's german made (it came with a german plate on the front), how can i find out? And what does that mean about the car? (besides where it came from).

Q 3: I have 3 gauges in front of the shifter, what the heck are they for?

Q 4: The previous owner gave me some previosly used coil-overs for front and back. She said they would lower it and inch or two. Would this fix my squeaky suspension?

Q 5: Is this car worth keeping? I love it when it works, but am tired of cleaning up the problems left by the last owner.

Any feedback is greatly appreciated!

If you look on the lower edge of the drivers door, either on the door itself or on the frame of the door opening in the body - you should see a plastic label giving the car's VIN #, its date of manufacture and place of manufacture. I dont know about GTI's, but I presume they were like Jettas; they were made in the U.S., in Mexico, & Germany, and made for the Canadian or U.S. or Mexican/Cent. American market, or the European market. And unfortunately they might all be different depending on where made and where they were meant for. There would be a U.S. Federal version, a U.S. high altitude version, and a U.S. California version for example; all slightly different under the hood. There were at least two engines available - the 8 valve and the 16 valve too. There should be an emissions info label on the front of the car, near the radiator.
I think they stopped calling them Rabbits in 1984, began calling them Golf and GTI's. They were about the same as the Jetta, but Jettas were 4 door and had a larger trunk. There were no Jetta convertibles, sad to say. (I have a 1990 Jetta).
You should get one of the service manuals that cover this car. You can get them on CD from a VW dealer, and they are pricey but will pay for themselves in the first weekend under the hood. The Robert Bentley complany makes manuals that cover the 85-92 GTI, Golf and Jetta. They show up on ebasy.com. I have one of those; they are pretty good, but there is still confusion due to the large number of model variations from year to year, country to country.
I suspect the only thing that will fix the squeaky suspension would be new struts.
I am guessing the 3 gauges on the console are; oil pressure, water temp, and volts. I believe that was the usual 'rallye' option. One of them migth have been a tach though.
The car is definitiely worth keeping - but whether its worth it to you is your decision. My perspective is that I like to do 'pre-emptive repair'. This means replacing or inspecting things just because they are old, and not waiting till they fail. It also means I get to do the work in the driveway, not having the car towed ($$$) to a garage ($$$) for work. In the case of most 21 year old cars, I would start by taking the car off the road for a couple of weeks, replacing all of the brake parts - like wheel cylinder and brake hoses and handbrake cables and springs. I would rebuild the calipers, probably replace the master cylinder. Then I might replace the radiator (which is a consumable, but gets used-up slower than tires and fuel), along with all hoses under the hood that carry hot water, and the thermostat and water pump. Then I could have piece of mind for ten years about the cooling system. Then I might replace all of the fuel hoses and the fuel filter. And so forth...
The old saying 'if it aint broke, dont fix it.' is nonsense to me. We take drives into hot, dry and rural regions of Mexico. I do NOT need to have my car die on me in the middle of the Coahiulan desert when it is well over 100°f in the shade - and there isnt any shade.