I just serviced the bottom bracket pressed in bearings on my new to me 1992 Merlin Road Ti. It has two tiny grease zerks that make it pretty easy.
The bike maybe had 250 miles on it when I bought it from its original owner. I used a Park fine point tipped grease gun, pummped grease
into the tiny zerks and by pumping the gun three times simply pushed the old grease out of the bearing. I used white lighting as it is a clear grease. Once I saw clear white lightening I knew that the old grease had been pushed out. The 1992 Merlin owners manual says grease the BB every thousand miles.
This was the first service BB service since 1992. I have traded emails with Tom Kellogg at Spectrum Cycles and he said they would be happy to install sealed bearings if I decided that’s what I wanted to do. Servicing the BB is pretty easy. Since the bike has so little miles on it...I may just keep it as is.

a few pics- the bottom pic..service cleaned up and done.