Expect to pay about $2500 for a used/rebuilt 3.0, and the rest of the quote is installation costs. If you don't have aproblem dropping $4k, and are willing to pay more, you should consider doing a 3.4 Tacoma engine swap. If you don't want to spend more than $k, you shoudl consider rebuilding the 3.0 you have. I would consider boring the block .020, or .040 over, and install some headers, with the rebuild. This should liven up the 3.0 and help it breath better. With the head/block true. a new head gasket and NEW headbolts, it should run you another 200k, and shouldn't be anymore(maybe less) than the $4k your mechanic quoted you. You can get a master rebuild kit from enginebuilders.com for under $400(includes larger pistons), headers will run you about $700(headers/rest of exhaust), plus block/head work, misc. items like knock sensor/wire, a pulley or two, water pump, etc.