There are no guides that i know about, however many users such as Jingle Fett are very good at textures in FPSC X10 and can help you out in many ways, i have created a fair few X10 ready textures but not for at least 6 months so im a bit rusty in that department.
A word of warning though X10 needs a min of 3 texture files for each model. D,S and N versions. It is hard to make all of these and especially hard to get them working in X10.
As for artists in the store there are many and there should be a check box in settings somewhere to only show X10 ready media.
All the best
Windows 7 Pro, Intel Core 2 Duo 2.8Ghz, 4GB DDR3, Dual nvidia SLI 9800GT 1GB, 1.5TB Hard disk