I can't comment on the length of time the VHPD engine will last but I certainly expect to get more than 30,000 miles out of mine, it depends how the car has been used - mostly road or as a track toy. Road use should put the engine under a lot less stress.
Your best speaking to someone like DVA power who will give you a labour cost and prices of parts are good should you need them. If your like me you will always go beyond the basic refresh but I feel about £2,500 would be a good contingency fund that would allow for a refresh with some performance enhancements included 😬
When I took my engine for rebuild (secondhand with no history) the total cost including new oil and water pumps bearing gaskets etc including an engine balance, head port and verniers was about £2,200. You then need the engine mapping at about £350 in you already have a programmable ECU and want to get the best out of the engine.
You can of course do it for less or spend considerably more, one area I would not cut out is the engine balancing, it took a lot to convince me but now I would not hesitate to have it done in future.
Andy