I suppose something like this: of course: change the position of the front of the buildplate according to your printer, depending of the size and where the centre of the zero point is positioned). Same for the value you use for extra prime and suck at layer change (now set as 1 and 1.1mm.) Also, set the speeds normally used. The F value is in mm per minute, so 50 mm/s is F3000
G1 Z<Z+3> F600 (lift the head 3mm)
G92 E0 (reset the E value)
G1 E-1 F600 (do an extra 1mm retraction)
G1 X0 Y-75 F2400 (go to the front of the buildplate 40mm/s)
G1 X100 Y-75 (go to the right)
G1 X-100 Y-75 (go to the left)
G1 X100 Y-75 (repeat go to the right)
G1 X-100 Y-75 (repeat go to the left as much as needed)
G1 E1.1 F600 (prime the nozzle again)
G92 E0 (reset the E value again)
G1 X<NEXTX> Y<NEXTY> F2400 (go above the next to print place)
G1 Z<Z-3> F600 (lower the head again?)
I don't know if that last line is necessary, as the next G1 command probably will contain the (new) Z value.
You can repeat the sweep movement depending how much time you need.
When not seeping at all you can use the G4 command (dwell) followed by how long (ms) you want to wait.
G4 P3000 is wait 3 seconds. Or in seconds: G4 S3.
Check if your firmware actually is using all that (common) commands.
Check the Gcode output first in Repetier Host, as the travels are visible there as well, to check if some command is sending your extruder crashing into a wall....
When using relative coordinates you have to use the G91 command, after that you can do whatever relative moves, but you have to do the math so that when ending all that relative commands the position of the head is exact the same as before the G91 command.
To go into absolute coordinate, use the G90 command.
Hope this gives a start.
Bart