You can get probe sequences and coordinates (usually) from the Affy website:

You'll want to extract the probe-level summarization and you can then plot intensity as a function of position with your genes of interest.

With respect to the probe-level summarization from the oligo package, the code should look something like this:

library(oligo)

celFiles = list.celfiles("/path/to/folder", full.names=T)
rawData = read.celfiles(celFiles)
probesetData = rma(rawData, target="probeset")
probeset.expression = exprs(probesetData)
probesets = rownames(probesetData)

However, selecting the optimal genes may be tricky. I've tried using the validated genes from this paper, but they didn't seem to show much of a position degradation effect (in the array data that I have checked so far):