Congrats on wanting a bigger engine. You have many choices on engines and I doubt you will have any tranny problems based on the power output from any stock d series engine. I would suggest you look at your cash flow and just figure out what would work best for you and your wallet. You might be better off doing this that would give you some more horses and should be a bit cheaper then going the full engine swap route. I would suggest you get some friends that have some skills in the garage so you can learn to wrench yourself, Labor is the most expensive thing when trying to mod you car. Where are you from, see what shops people on the forums use in your area and call around for some estimates. Your best bet to get what you want is www.thepartstrader.com you can find some damm good deals on there. 1 thing you should remember is the fact that your auto tranny will not last long if you decide to beat it up with neutral drops and crazy downshifting so be good to it or you will be very pissed when you have to replace it.