Hi sn17,
I haven't done the Stinson wreck walk, but from all accounts it is a very demanding bushwalk and 34 km in one day is no easy feat (particularly when the track you are on is heavily overgrown with various rainforest obstacles). I have done many walks in Lamington NP, however, and would recommend doing any (or many) of these other options in preparation. Since you are planning to do the Stinson walk in a single day, you will probably need to prepare by walking full-day walks, and after you build up your fitness, try and do them as quickly as possible - any of Toolona Creek Circuit, Albert River Circuit, the Border Track, Shipstern Circuit, Coomera Falls Circuit would be a good start. Very full-day options could combine Shipstern with Dave's Creek and Upper/Lower Balanjui falls, or combine Coomera Falls with Mt Merino/Mt Wagawn/Araucaria Lookout (both in the Binna Burra section). You could also add Mt Merino to Toolona Falls from Green mountains section. Many variations are possible at Lamington, see the following rough maps for a starting point:
Green mountains section -
http://www.nprsr.qld.gov.au/parks/lamin ... ns-map.pdfBinna burra section -
http://www.nprsr.qld.gov.au/parks/lamin ... ra-map.pdfI also haven't done Bullant Spur track to Blue Pool, but if I remember correctly, this is 'off-track' and you should carry a topo map and compass (if possible, go with someone who's done it before!).
If you haven't been before, Lamington NP offers some of the best rainforest bushwalking in SEQ. Training doesn't need to be a pain, you'll really enjoy your walks here in rain or shine. Be aware that you will encounter many leeches in the wet/if you do any of the creek circuits.
Of course there are plenty of other options for walking in SEQ. If you have a good chunk of time before your walk and are looking for some variety, I can suggest more places to visit/walks to do.
Cheers,
Munch