OK, just so you'll know, this has been available from that source since quite some time ago. Trustworthy advice I received as a result of a private inquiry back then indicated the following: (1) The service manual and the service application are Epson proprietary materials that Epson provides only to designated service outlets; they are not in the public domain and all other distribution of them is not authorized. Epson will not provide them to users like us. (2) As well, copies being marketed on the Internet may not be exactly correct in all respects or may not in all cases correspond with the details of the printer model it is intended to cover, because the manuals undergo periodic revision, hence there are usually a number of versions of the same basic manual. (3) It takes training to be able to use these materials properly - some routines being less straightforward than others, even with the manual and the software.
So, having learned that (a) it's possibly not "legal", (b) it may not be the most appropriate version, and (c) using it could be beyond my pay-grade resulting possibly in even more costly service calls than otherwise, being perhaps quite a risk-averse individual I decided to pass on it. Having seen my 4900 opened up a couple of times, I've decided to apply the theory of comparative advantage to printer repairs and use my time otherwise; but YMMV. Would be interesting to hear of successful outcomes from those who have used these materials to do whatever on their 4900s, without prior training.