Apologies in advance if this sounds noobish, and for my lack of knowledge of technical terms (I'll probably use 'thing' a lot). I'm actually a learner driver, but I own a car ('96 Holden Astra, automatic) and am going for my provisional license in a couple of weeks.
I have a problem with my car's gear shift. Often the gear shift will just slide back and forth, and not lock into any gears. I've discovered under the hood that this is controlled by an arm with a round plastic thing on the end, which clicks onto a nub on a metal arm which changes placement according to what gear the car is in. Often the round plastic bit will detach from the metal nub, and I'll have to click it back in place myself. This has been really annoying because it will seemingly do this at random, I've had to put on my hazards and click the thing back into place in parking lots, in the middle of the street after reversing out of a parking spot, at intersections, etc.
I've been to a mechanic about this problem, and he told me that all they could do to fix the problem would be to replace the entire arm, which would cost me about AU$500. Since I can still drive the car okay and all that's required to get it going again is to click the arm back into place, I opted not to spend the money. I'm reconsidering now though, as I will be doing my provisional license test in this car and I don't know what my testing officer's reaction would be if my car decides to do its annoying thing during my test.
My question is - is there a way I could fix this myself for cheaper? It's been suggested to me that I could duct tape the arm to the metal nub. I'm not sure if this would work/be safe though? Could anyone give me some advice?
Here's a (bad) diagram of the part of the car I'm describing. Fig. A is how the gear shift part should look when the arm is hooked on properly to the metal nub. Fig. B is how it looks when the round plastic bit pops off (the black dot is the metal nub). Sometimes I will have to play around moving the gear stick to get the bar with the nub into a position so I can get the plastic bit to hook onto it again.
Also, I almost always have to start my car in neutral because it doesn't lock into park properly. Obviously this is related to the gear shift problem in some way. It'd probably look bad if I had to start the car in neutral for my test. -_-
edit: picture of the actual bits