The tools I used were simple:
Choosing the crystal and capacitor:
Pretty much any 32.768 kHz crystal of the right dimensions will do. Usually you will find them under "watch crystals". I used the Abracon AB26T: http://www.abracon.com/Resonators/AB26T.pdf
Choosing the capacitors:
For information on attaching a crystal and capacitors to the AT91SAM7L processor used in the HP-20b/30b see this application note page 9:
Total capacitative load on the crystal is the 2 external capacitors in series (as far as the crystal is concerned, the ground connects C1 & C2 in series to itself) + the capacitance of the processor and stray capacitance in parallel:
CL = (C1*C2)/(C1+C2) + Ci + Cs
CL = the capacitative load on the crystal
C1 & C2 are the 2 external capacitors we are going to add
Ci = internal capacitance of the processor for the crystal pins
Cs = stray (track & PCB) capacitance
If we keep the 2 external capacitors the same value: C1 = C2 = C
CL = C/2 + Ci + Cs
From the Atmel app note above: Ci = 2.5pF
From the crystal data sheet: CL = 12.5 pF
Cs estimated ~1 pF
thus C = (CL - (Ci + Cs))*2 = 18 pF
The Atmel datasheet specifies a maximum of 20pF, so 18pF is in the ball-park.
http://www.atmel.com/Images/Atmel_6257_32-bit-ARM7TDMI-Microcontroller_SAM7L_Datasheet.pdf (section 35.4.3 table 35-15).
For choice of capacitor, I avoided Y5V in this application as they have a wide capacitance variation with temperature which will alter the frequency of the crystal - not what we want for a stable clock.
I would recommend X7R or NP0/C0G. I used Multicomp - MC0603N180J500CT - (MLCC, 18pF, 5%, 50V, C0G / NP0, 0603).
(Note 0603 is the imperial size SMT, in metric it would be 1608. Be careful to check when ordering!!)
OK, so now for the mounting. I did the capacitors first and the the crystal.
Here are a video I made mounting the first capacitor:
(Note, I am not a professional solderer, but a home hobbyist)
The final product:
I hope you have fun doing yours :-)
(I ordered my crystal and caps in bulk, so have about 100 spare sets. Anyone want some for postage only, see eml below. Each set will have 1 crystal and 4 caps).