OSV went splat

[house808]

Hi All,
started the X5 4.4 (it's a 2002 with 100,000 plus) last week and got the tell-tail sign... thick white smoke for 20sec. then clears up and runs/idols fine... my indi-mech can't get to me till thur. (4 days) So, I babied it to work (15 miles on freeway) and seems to be ok, but I live in the hills and at the end of my commute going up hill if I use more than one inch of throttle it will missfire and blow another puff of smoke, so I just creep up @ 1200 RPM's
Couple of questions for the veterans..
1. my mech quoted me $450. for the whole job including new OSV and intake gaskets. Is this a good/fair rate?
2. is limping it to work like this for a few more days going to foul the CATS and or O2 sensors beyond what a good hard flogging will blow out when shes fixed?
3. anything I can do to keep from causing any more dammage than I already have?
4. is there anything I should replace while I have it opened up? i.e. valley pan gasket, or is it on a replace as needed basis at this point?

Thanks for any help, I just don't want to turn a $450 issue into a $2500 issue...