Best way to correct/add data from WeatherLink

[Weather or not]

New to the WD program, I imported data from Weather LInk for the month of April.  In attempting to import prior months, I messed up a couple of hours of April 28th data - it shows things that didn't happen (It shows rain; there was no rain/ it shows cold temps; there were no cold temps).

Questions:

1.  Is it possible to go into the data files and correct the several hours worth of data from yesterday; if so, how; what are the file names I should look for the anomalies in?  And is it worthwhile to do that compared to other corrective measures?

2.  What is the best method to cleanly import data from the Davis datalogger for at least the first 4 months of this year?  Whatever method I used to import the April data previously it was luck via trial and error.  Is it best to eliminate the existing data files and start over?

[Weather Display]

edit the logfile for that month directly (e.g using notepad.exe)
e.g 42012lg.txt for april 2012
then save the changes
then use action, convert WD logfiles to data files, select that logfile, then click on convert
then click on recreate last 31 days data file

[Weather or not]

edit the logfile for that month directly (e.g using notepad.exe)
e.g 42012lg.txt for april 2012
then save the changes
then use action, convert WD logfiles to data files, select that logfile, then click on convert
then click on recreate last 31 days data file

"edit the logfile for that month directly..."  Is this referring to the WD files or the WeatherLink files? 

I have several 42012 files in my logfile folder.
Here is a list of them:

42012currentcostlog
42012growlogten
421012lg
42012lgsun
42012lgten
42012vantagelog
42102vantagelogten

They are all txt documents.  Are there too many?  Should I delete any?
 I selected the 42012 file to revise to eliminate erroneous rainfall.  I changed the extraneous rainfall to zeros.  I converted that WD log file to data file.  I closed the program, and reopened it.  It still shows yesterdays' rainfall at .012 inches despite changing April 28 to all zeros for rainfall in each entry.

Finally, I am having difficulty importing DataLink files before 2012 to WD.  What am I missing?

[Weather Display]

e.g 42012lg.txt for april 2012

tht gives an example of the file name to edit

re rainfall, you can set the needed rain totals under control panel, offsets and initial rainfall
for individual day totals edit, there is a FAQ on how to do that

re .wlk import for prior years, see if a WD log file was created for that year...then convet that to data file, as per above