You will need to get the car scanned or buy an OBD2 scan tool for the car to tell you what's wrong. Then you can report back here once we have more info.

Your local computer repair shop or mobile phone repair shop would have some lying around from old units they can just throw at you... won't cost you anything.

I understand you want to change the shift pattern for your vehicle. You may have changed wheel sizes, for example, and want an easy way to adjust the thresholds without the hassle of swapping out chips on your auto trans unit. Depending on what part of the world you're in, Jaycar Electronics has a module you can just wire in. They're not showing it on their website, so I'll check back through paper catalogues for a part number for you.

I've always found the Auto Wreckers will do it cheaper than most. The cheapest of these will let you take it off yourself using your own tools. The biggest of these here is U-Pull-it, but you will need to check locally where you are. Go to their website first and check their stock lists to hunt for your make & model or research to find equivalents that fit your vehicle. Some you can call to check if they have stock.

Join the cut wires together. Have you seen the seven other questions for the same device?

Have you seen this one? Looks easy enough, no? https://www.youtube.com/watch?v=9npIN_un...

Common problem. Check first if it's the battery or the charger, then check battery voltages. May need a new battery.

Assuming you've tested the switch and tested the lights separately, and the wiring is okay (problem doesn't come & go when you move any part of the wiring loom around). Then it's likely a Body Control Module issue (common problem) on this one, and quite a few others too. The quickest way is to buy a change-over unit from a parts supplier (repaired, tested and under a good warranty - & cheap enough). I wouldn't recommend second-hand, as these are a common problem for years. If you want to repair your own, you'll need a de-solder station & soldering iron with adjustable temperature. Re-work any dry joints you can find (especially on connectors and relays) and clean out the PCB relays (difficult to get exact replacements for). Use a 5mm strip cut from thin card and pinch it gently between the relay contacts while drawing it through until you can't see a black carbon trace on the card any longer. I've personally fixed hundreds of these and many more like them. If you need help repairing, post photos of both...

Common problem with the Body Control Module (BCM) on this one, and quite a few others too. The quickest way is to buy a change-over unit from a parts supplier (repaired, tested and under a good warranty - and cheap enough). I wouldn't recommend second-hand, as these are a common problem. If you want to repair your own, you'll need a de-solder station & soldering iron with adjustable temperature. Re-work any dry joints you can find (especially on connectors and relays) and clean out the PCB relays (difficult to get exact replacements for). Use a strip cut from thin card and pinch it gently between the relay contacts while drawing it through until you can't see a black carbon trace on the card any longer. I've personally fixed hundreds of these and many more like them. If you need help repairing, post photos of both sides of the BCM PCB.

Have you checked the surfaces you applied the new gaskets to, as well as all hose nipples? Look for hair-line cracks and score marks from the removal tools. Hose nipples can be made from a softer metal like brass (which can also be plated to make it look like something harder). Softer metals are very easily scored by a knife or other hose removal tool and you will always get a leak when those marks score a line through the serrated nipples. You will need to file down through the mark, but in such a way that preserves the exact shape of the step. If you muck it up, buy another nipple (cheap). Never assume that because a professional has done the job and tested it, it can't be done in a rushed, cheap manner. I've seen literally hundreds of nipples scored like this and they all deny doing it.