Valve seal question

[Feelstranger]

Hello all,
I have not been subscribed to this list for a while (year?), so I hope this 
is not an anoying question.  I looked at the archives and tried to search 
them to no avail.  I am getting significant oil consumption.   I have seen 
the small puffs of smoke at shifts while tailing my SO.  I gather this is 
typical of valve seals, correct?
I was going to have a shop do them, but they said it was a waste and that 
the exhaust guides should be done too.  Car is at 163K.  So, is this likley 
true?  Can valve guide wear be tested without head removal?
How hard is a valve seal job only on a 20V?  I assume it can be done with 
head in car?

Thanks!
Nat