Piston boot is pretty bad to fit unless you've had a few hours practise doing it and even then the fit of the circlip doesn't look very satisfactory:
I'm not quite sure how you're supposed to get the internals of the OEM piston out to use for the replacement Budweg piston. Unless you've got a very specialised tool I think you'll need to carefully cut the piston about 10 mm down (I used a large high power abrasive cut-off saw, not sure if a lathe would be a suitable alternative, a hand held angle grinder would work but will take you ages) in order to get access for tools like mole grips, levers or grinders. I accidentally cut it very slightly too fine (allow a good few mm incase it slips in the vice due to vibration) so in the end I just levered the plate out - I'm not sure whether it will actually just twist out.
I believe the rubber centre of the cap at the back of the glide pin is actually a pressure relief valve to release any trapped air or grease.
Recon caliper is 73 pound + 30 pound if old one not returned + VAT. If your caliper is young and in good nick and your time is not a issue, a new piston and seal may possibly be a better solution than a recon caliper that may have come from a very old car and had a lot of wear. DIY rebuilds probably just have a bad reputation because people don't replace the pistons and don't obtain the special rubber grease or don't clean the bore properly. The seal moves on the piston, not the bore, and theres plenty of play, so condition of the bore doesn't have to be a mirror perfect finish (in fact theres machining marks on a brand new one comparable to a slight bit of rust damage). Incidentally the photos show the caliper bore before it was cleaned up, but it was taken appart to replace the piston and a torn boot, not because it was sticking.
You're supposed to use a special service tool if you want to disassemble the handbrake mechanism in the caliper body according to the RM182E Toyota repair manual. The circlip is quite deep down also. Consider just getting a recon caliper if you think the O-ring inside or the handbrake crank seal actually need replacing, from a cost of your time point of view as much as anything.
Many thanks to Darrell at Brakes International Ltd, for twice urgently sending me urgently needed inexpensive parts. Trade prices too, totally recomended. See www.brakesint.co.uk (afraid you need to register and install shockwave flash), phone 01254 695695 with credit card once you know what you want (by all means mention you saw them recommended on mr2turbo dot info).
A set of OEM brake calliper rubber parts for the rear, both sides, is about 85 pound from Toyota, and you can't obtain the parts indivdually (so if you tear a boot thats another 85 quid). I wouldn't like to think what they charge for a piston. I'd give genuine parts a miss for this one, especially considering the sharp contrast between the service of Brakes International and Toyota GB.