I get a big blue cloud of smoke (out the exhaust mainly, not the breather so much) when I start her, and a steady stream of smoke from the breather after that. She misfires quite a bit and the oil pressure light comes on at low revs once she's warmed up. She's got a tendency to conk out when idling (not good with an auto - I'm becoming quite a tap dancer) but still feels like she's got a decent amount of power. Although I'm no mechanic I know the symptoms mostly sound like worn rings and/or liners, so I'm wondering what to do about it.
My dad's old Reliant had this problem years ago and I remember it used to overheat quite badly once it started doing this. This worries me - I've not got a temp gauge so I always wonder just how hot she's getting and how much harm I'm doing. I'm also scared to take her for longer trips now because I'm not sure how long I can reasonably expect her to keep going (and I'm also wondering if I should stop running her and get it sorted sooner rather than later of course to avoid really killing the engine).
I believe I've basically got three options: get it repaired, get a reconditioned or second hand engine, or sell the van on to someone who knows more / has more to spend (being totally honest of course about the state of the engine). To give you an idea of the rest of the van, the underside looks good (I should know, I've spent the last three weeks down there!) and there's mainly just some superficial looking rot around the arches and the bottom of the sliding door. Everything else (except the heater) is fine.
What do you think? I know the repair would be an engine-out job (beyond me, I don't even have a lockup) but haven't had a quote for it. I can get a recon engine for about £1500 (ouch), not sure about cost to fit it or even deliver it. If I was selling I think I'd let her go for about £500 (but it would break my heart

Any advice would be massively appreciated. Thanks in advance.