Hi
agree with Brien.
My first google came up with the company with hundreds of user/service manual.
I have bought long time back semi industrial 1972 Phaff which was a model with the 3 step zigzag which kites use
which is a must have stitch (stretchy but super strong.
If u take it to get serviced get a quote first,super expensive.
Over the top threads are Tenara brand which gives 20 year garrentee.
check out sail rite brand in USA they have heaps of videos other than that like the man said just dive in with manual and give it a go but read,read,read first.
Ive been doing all my own repairs for years even a couple of leading edge tears.
After keeping track of my time the repairers are really cheap except your kite is back in action quicker with no waiting for it to get done and post back and forth.