For a high quality inexpensive sealer I like Hydrex by Tenax. It's easy to use, just wipe it on, let the residue evaporate and apply a second coat. It leaves no residue and does not affect the shine, color or hue of the stone.
As far as your lippage is concerned, sanding it down 1/32" and bringing back the polish is not something a novice should do. Top polishing or flat polishing is best left to a pro with experience doing that as it is much harder to make it look right than it appears.
Here is a link to Hydrex Sealers:
http://www.defusco.com/Glues:-Epoxy,-Polyester,-etc.-Hydrex-Sealer/c82_502/index.htmlGlad to be of service,
Mark