I have a 91 LS 400, and i need to replace my valve cover gasket. My local shop quoted me $750 parts and labor, does that right to you guys?

That sounds like A LOT. I've done valve cover gasket jobs before (not on the LS400), but they dont take more than 2-3 hours, and the parts dont cost more than $100. In fact, most gaskets are around $20 per side.

Perhaps one of the lexus tech here can chime in with quotes.

Yea, i feel like that is a lot to pay. And its not at a dealership, its a quote unquote "lexus car care place". I had plenty of work done at this place and i've been very happy with the service. but dang 750 seems a little steep to me.

It is steep .. You can get it done for nearly half that. It isn't a difficult procedure, so going to most any certified master indies should be fine.

Is this something that I can do myself?

you can do anything with the right tools

There's a tutorial on lexls.com on changing these gaskets. Very simple straight forward job.

labor guide says 3.6 hours... at an average of $80 / hour, $288 in labor, and $56 in parts...

id do it for $200 with part if you were local...