I wouldn't compare rebuilding a DPSS laser to building an optical train in a projector, although there are likely some very complex optical paths out there which do rival it. The tolerances involved in the alignment and construction of DPSS lasers are very tiny, so extreme precision and patience is a must. It's not unheard of to hear of guys spending days tweaking the alignment of their laser for optimum output. Output power, mode stability and beam quality are all factors which need great care and attention and usually require a lot of tweaking before they're just right.