How many RAM chips do I have in my A1342 MacBook Uninbody

As mentioned, if you have the original configuration you have two 1GB sticks of RAM. 1 in each of the only 2 RAM slots on the logic board. That doesn't help you much if you are not the original owner. Click here for a guide that will show you how to verify what is actually installed on your machine.

The answer to your 2nd question depends a lot on how you use your laptop and your plans for future upgrades. There is a noticeable benefit to having matched sticks of RAM installed during RAM or CPU intense processes, such as booting, opening a program or using a program that is RAM or processor intense - watching flash videos, video re-encoding, etc... So with matched RAM your laptop will be more responsive - boot faster, open programs faster, which means less drumming of the fingers waiting on something to happen and less lag using processor and RAM intense programs. The "Apple Gurus" that have done benchmarking of the benefits of matched RAM have avoided the time differences of opening programs and the boot process. Nor do they talk about streamed video. They stick with web surfing and various less demanding programs. To a certain degree I see why, because once most programs are open the benefit of having matched RAM are negligible. If you don't mind waiting an extra 30 seconds or so for your laptop to boot or open a program then matched sticks of RAM might not be so important to you. The next factor to consider is the cost of future upgrades. If you get the 4GB chip now you will spend less later when you decide to add more RAM. Over all adding more RAM, matched or not, gives an overall increase in performance.