an engine rebuild could seem quite daunting, i rebuilt my 260 5 years ago. apart from a rebore and a head shave i did all the rest myself and it cost $2200, that included pistons aswell. the easiest way to make sure that your not getting ripped of is to get a price from a few auto shops on a full rebuild kit, which wont include pistons, that way you will at least know the parts cost. If you are taking the block in yourself, you are only a few bolts away from doing the job yourself, as your block will only need a home and your crank will generally be in an alright condition. if you have basic machanical knowledge or knows someone who has and get youself an automotive repair manual or a L-series rebuild manual, available on ebay, and follow them, you will have no trouble whats so ever on building your own engine.
As mechanics will charge upto $80+ an hour, minimum 10 hours for a rebuild, plus any other unforeseen extras. so it could be quite a money saving option to do it yourself. Plus you will always have these pages to ask questions.
cheers,
Tony