Lance may well have expensive lawyers at his disposal
If Armstrong's to be taken at his word (!) then he's not going to contest so any lawyer involvement would be basic procedural, legalities and such like.
If he chooses not to contest then he's basically accepting the evidence as presented and the USADA panel will judge on that basis. That is, little that'd equate to a trial procedure. We'll know soon enough whether he decides to contest as he has to file his response before the end of this month (20th or 25th??).
Of course, come the hour, whether he sticks with his previously stated decision of not contesting (and several commentators have remarked on this point already) is another matter. It'd certainly be atypical. It's possible that he's decided to accept any outcome in the name of getting on with his life. Whilst not what we might expect of him, given his character, I think it would be none-the-less understandable.
For me, a factor is any ban he might face. Given the nature of the evidence, it's hard to see anything other than a life time ban (that is, if USADA decide to go ahead and that, I think, we can assume is likely). That scuppers any notion Armstrong may have had about continuing triathlon (unless he can find some organisation/competition NOT signed up to WADA). Whether Armstrong factored in not being able to compete in triathlon as a likely outcome, I obviously don't know.