if I were getting my T-belt and water pump replaced at 180k miles, how much additional work (labor) is involved in getting at the head gasket and repairing/replacing it?

my brother slightly overheated my LS montero by wheeling it pretty hard and I noticed some disappearing coolant and some white smoke. the dealer gave me a quote, but I want to keep them honest by asking some DIY guys on here.

this is on a 97 Montero LS

TIA
Scottie

97 Montero SR w/Mitsu Adj Shocks & Rear Diff Lock ARB Front Diff Lock 4.9 Ring/Pinion 3.15 transfer box 43:1 crawl ratio 2" suspen lift 2" body lift 2" Gas Tank Lift 35x12.5 MTRs 15x10 Wheels Rock Sliderz ARB front bumper w/12k winch Custom rear bumper