Music Composers Unite!
What are you going to sample?
Any of the popular DAWs will work for this. I am familiar with Logic Pro for Mac: it has the EXS-24 software sampler built-in so I can record samples and then play them back to check them. However, familiarity is probably worth more than any absolute technical difference when it comes to choosing DAWs.
For interfaces, I think it's worth getting a 96kHz/24 bit interface for maximum sound quality. There are many available, if you only need to record acoustic guitar, you could get one with just a couple of channels and economize. I have not found any brand to give a noticeable difference in sound quality, but there are others who would argue this point. If it exists, it is very subtle.
A condenser mike is a good choice, a ribbon mike is also good for lower-volume instruments like acoustic guitar. I think you would notice the difference between mikes more than any other factor other than your recording environment. I know there are people who would never record with anything less than a $1200 Neumann, but I've got very good results with Shure Beta 87As, which usually go for around $250.
One caveat: creating a complete library of sound samples is a laborious process, with creating recordings at different sound levels from different ranges of the instrument, editing the samples and creating a uniform sound among all of them. If this is what you want to get into, I would suggest first trying it with the equipment you have now to see if you actually have the patience for the process.