Since u ask, I tell u my experience nia. Question me back in a sarcasm isn't gonna help. Moreover, ayam troubleshoot over thin air, I can't possibly know what and where went wrong. Shakeyness as u claimed, izit forward vibration or side way wobbling? The shakeyness as claimed by u can be many other issue like follow:
1) Tyre pregnant
2) Clutch plate wear off
3) Clutch cover lost tension
4) Rim bengkok
5) Driveshaft bearing ko
6) Driveshaft retainer spring detached/snapped
7) Flywheel bengkok
8) Dog clutch gears wear off
U see, other than item no.8, none of them are directly involved in the transmission box. Hard to bang gears usually is item no.3. Since u so determined its gebox plobrem, regardless where u sent ur car to, the technician will agree with u bcoz they get to charge u a price of gebox replacement, whereas could possibly be item no.6, open driveshaft boot, place back the spring in place. Reinstall it back & give u a bill of RM2k for "change gebox"
I'm not saying ur car shake due to other fluid is leaking,I'm just saying it could be other stuff that is leaking. Since now oni u tell me u saw oil leaked from gebox section then fine la. Does leak means vibration? Does vibrate means must be from gebox since its leaking? So, in the end its your car, your money. I'm just trying to help. Sometimes repairing car is not about how close the shop is, its how reliable they are. U know I know Shawie need special care by Renault specialist, u sumoar wanna find some ordinary workshop to work on your car? Fine la go ahead & "change gebox".
Don't get me wrong. I'm not angry. Just being worried/anxiously trying to save u from being chopped. That however didn't count if u have decided ur gebox needed to be "overhaul/so called changed" by your nearby professional, I can't stop u though.
How marj per donut

.Dont get mad,im just telling what I saw on my shabi only.
No 1 and 4 definately out.The rest is possible.Does oil leakage in gearbox will cause gear to shake while driving or not?Definately not going to a workshop and tell the foreman my gearbox got problem bro,since I also donno what is the real problem.Just discussing it here with you guys here since all of you have experience on repairing,mods and etc.