Yes it's safe, but I'd recommend a P4 1.8GHz w/512K of cache which you could easily up the FSB to 133 leaving you with a 2.4GHz system with 533FSB usuing only retail heatsink and fan. You can get this in a retail package (comes with approved fan and heatsink) for $164 from newegg.com.
This way you have a <b>much</b> better processor that has shown to easily overclock w/o any issue.
I have a via motherboard similar to yours. It only overclocked my 1.8a about 10%. I would recommend an sis 645 or 645 dx board for overclocking. I got an asus p4s533 mobo (refurb from newegg) and it overclocks that same cpu by 33% with no problems in jumper mode. A faster solution for you would be an xp1600 (54.99 shipped at newegg) with any kt266a or kt333 board. Both can be had for less than what you'll spend on the celeron setup, assuming you already have ddram.