There is a SAL1855 service manual here
Actual link is via "Get Manual" at lower left of page - appears authentic. 40 pages in English and 78 total. Attempting to just copy download address directly failed - they control free downloads to 2 per day and that is probably part of their mechanism for doing so. It would be interesting to see what else they have.
NB - Note their comment - "This lens can disassemble both the 1st lens side and the mount side". I take that to mean that you can legitimately gain access from either end. You may wish to consider what is probably wrong with your lens and whether partial disassembly from one end or the other may work best. The magnificent exploded assembly diagram should help with these prognostications.
Disassembly section starting on page 2-1 looks extremely helpful. You will (probably) have to improvise their "special tool" universal wrench - a pair of drawing compasses with two sharp points or a wide opening circlip pliers may suffice.
larger version of above image here or see above referenced manual.
Cheap it may be. Totally simple it isn't.
Much larger version here or see above manual.