Hm... It is very hard to me to explain something on English, because it isn't native for me. But I will try.
NOTE: I am strongly recommed to create database backup before any expirements!
The most easies way to convert your data with saving all comments is using SQL. I do not use LyftenBloggie and I do not know it's database structure but I think it could be converted to jos_content via some SQL query.
Regarding comments... They are stored in jos_jcomments table. The comments posted in LyftenBloggie will have 'com_lyftenbloggie' in 'object_group' field of jos_jcomments. And in 'object_id' field the LyftenBloggie article's ID is stored. When you move articles from LB to com_content, they will got new IDs...
So to move comments from LB to content you have to change 'object_group' to 'com_content' and 'object_id' to new values. How you can get new values of IDs? The simplest way is remember last ID from jos_content (for example it 100 - so jos_content does not have any article with ID greated than 100). In this case you can edit your SQL-query and set new ID as old + 100.
In my mind you should use something like this (note, I do not sure about jos_bloggies_entries fields):
insert into jos_content(id, title, introtext, fulltext)
select id+100, title, introtext, fulltext
from jos_bloggies_entries
So if your LB entries had IDs like 1, 2, 3 and etc, in jos_content they became 101, 102, 103...
And after you convert entries, you could convert comments with query:
update jos_jcomments
set object_id = object_id + 100, object_group = 'com_content'
where object_group = 'com_lyftenbloggie'
I hope this help you...